| // SPDX-License-Identifier: GPL-2.0-or-later |
| /* |
| * fs/eventpoll.c (Efficient event retrieval implementation) |
| * Copyright (C) 2001,...,2009 Davide Libenzi |
| * |
| * Davide Libenzi <davidel@xmailserver.org> |
| */ |
| |
| #include <linux/init.h> |
| #include <linux/kernel.h> |
| #include <linux/sched/signal.h> |
| #include <linux/fs.h> |
| #include <linux/file.h> |
| #include <linux/signal.h> |
| #include <linux/errno.h> |
| #include <linux/mm.h> |
| #include <linux/slab.h> |
| #include <linux/poll.h> |
| #include <linux/string.h> |
| #include <linux/list.h> |
| #include <linux/hash.h> |
| #include <linux/spinlock.h> |
| #include <linux/syscalls.h> |
| #include <linux/rbtree.h> |
| #include <linux/wait.h> |
| #include <linux/eventpoll.h> |
| #include <linux/mount.h> |
| #include <linux/bitops.h> |
| #include <linux/mutex.h> |
| #include <linux/anon_inodes.h> |
| #include <linux/device.h> |
| #include <linux/freezer.h> |
| #include <linux/uaccess.h> |
| #include <asm/io.h> |
| #include <asm/mman.h> |
| #include <linux/atomic.h> |
| #include <linux/proc_fs.h> |
| #include <linux/seq_file.h> |
| #include <linux/compat.h> |
| #include <linux/rculist.h> |
| #include <net/busy_poll.h> |
| |
| /* |
| * LOCKING: |
| * There are three level of locking required by epoll : |
| * |
| * 1) epmutex (mutex) |
| * 2) ep->mtx (mutex) |
| * 3) ep->lock (rwlock) |
| * |
| * The acquire order is the one listed above, from 1 to 3. |
| * We need a rwlock (ep->lock) because we manipulate objects |
| * from inside the poll callback, that might be triggered from |
| * a wake_up() that in turn might be called from IRQ context. |
| * So we can't sleep inside the poll callback and hence we need |
| * a spinlock. During the event transfer loop (from kernel to |
| * user space) we could end up sleeping due a copy_to_user(), so |
| * we need a lock that will allow us to sleep. This lock is a |
| * mutex (ep->mtx). It is acquired during the event transfer loop, |
| * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file(). |
| * Then we also need a global mutex to serialize eventpoll_release_file() |
| * and ep_free(). |
| * This mutex is acquired by ep_free() during the epoll file |
| * cleanup path and it is also acquired by eventpoll_release_file() |
| * if a file has been pushed inside an epoll set and it is then |
| * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL). |
| * It is also acquired when inserting an epoll fd onto another epoll |
| * fd. We do this so that we walk the epoll tree and ensure that this |
| * insertion does not create a cycle of epoll file descriptors, which |
| * could lead to deadlock. We need a global mutex to prevent two |
| * simultaneous inserts (A into B and B into A) from racing and |
| * constructing a cycle without either insert observing that it is |
| * going to. |
| * It is necessary to acquire multiple "ep->mtx"es at once in the |
| * case when one epoll fd is added to another. In this case, we |
| * always acquire the locks in the order of nesting (i.e. after |
| * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired |
| * before e2->mtx). Since we disallow cycles of epoll file |
| * descriptors, this ensures that the mutexes are well-ordered. In |
| * order to communicate this nesting to lockdep, when walking a tree |
| * of epoll file descriptors, we use the current recursion depth as |
| * the lockdep subkey. |
| * It is possible to drop the "ep->mtx" and to use the global |
| * mutex "epmutex" (together with "ep->lock") to have it working, |
| * but having "ep->mtx" will make the interface more scalable. |
| * Events that require holding "epmutex" are very rare, while for |
| * normal operations the epoll private "ep->mtx" will guarantee |
| * a better scalability. |
| */ |
| |
| /* Epoll private bits inside the event mask */ |
| #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET | EPOLLEXCLUSIVE) |
| |
| #define EPOLLINOUT_BITS (EPOLLIN | EPOLLOUT) |
| |
| #define EPOLLEXCLUSIVE_OK_BITS (EPOLLINOUT_BITS | EPOLLERR | EPOLLHUP | \ |
| EPOLLWAKEUP | EPOLLET | EPOLLEXCLUSIVE) |
| |
| /* Maximum number of nesting allowed inside epoll sets */ |
| #define EP_MAX_NESTS 4 |
| |
| #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event)) |
| |
| #define EP_UNACTIVE_PTR ((void *) -1L) |
| |
| #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry)) |
| |
| struct epoll_filefd { |
| struct file *file; |
| int fd; |
| } __packed; |
| |
| /* Wait structure used by the poll hooks */ |
| struct eppoll_entry { |
| /* List header used to link this structure to the "struct epitem" */ |
| struct eppoll_entry *next; |
| |
| /* The "base" pointer is set to the container "struct epitem" */ |
| struct epitem *base; |
| |
| /* |
| * Wait queue item that will be linked to the target file wait |
| * queue head. |
| */ |
| wait_queue_entry_t wait; |
| |
| /* The wait queue head that linked the "wait" wait queue item */ |
| wait_queue_head_t *whead; |
| }; |
| |
| /* |
| * Each file descriptor added to the eventpoll interface will |
| * have an entry of this type linked to the "rbr" RB tree. |
| * Avoid increasing the size of this struct, there can be many thousands |
| * of these on a server and we do not want this to take another cache line. |
| */ |
| struct epitem { |
| union { |
| /* RB tree node links this structure to the eventpoll RB tree */ |
| struct rb_node rbn; |
| /* Used to free the struct epitem */ |
| struct rcu_head rcu; |
| }; |
| |
| /* List header used to link this structure to the eventpoll ready list */ |
| struct list_head rdllink; |
| |
| /* |
| * Works together "struct eventpoll"->ovflist in keeping the |
| * single linked chain of items. |
| */ |
| struct epitem *next; |
| |
| /* The file descriptor information this item refers to */ |
| struct epoll_filefd ffd; |
| |
| /* List containing poll wait queues */ |
| struct eppoll_entry *pwqlist; |
| |
| /* The "container" of this item */ |
| struct eventpoll *ep; |
| |
| /* List header used to link this item to the "struct file" items list */ |
| struct hlist_node fllink; |
| |
| /* wakeup_source used when EPOLLWAKEUP is set */ |
| struct wakeup_source __rcu *ws; |
| |
| /* The structure that describe the interested events and the source fd */ |
| struct epoll_event event; |
| }; |
| |
| /* |
| * This structure is stored inside the "private_data" member of the file |
| * structure and represents the main data structure for the eventpoll |
| * interface. |
| */ |
| struct eventpoll { |
| /* |
| * This mutex is used to ensure that files are not removed |
| * while epoll is using them. This is held during the event |
| * collection loop, the file cleanup path, the epoll file exit |
| * code and the ctl operations. |
| */ |
| struct mutex mtx; |
| |
| /* Wait queue used by sys_epoll_wait() */ |
| wait_queue_head_t wq; |
| |
| /* Wait queue used by file->poll() */ |
| wait_queue_head_t poll_wait; |
| |
| /* List of ready file descriptors */ |
| struct list_head rdllist; |
| |
| /* Lock which protects rdllist and ovflist */ |
| rwlock_t lock; |
| |
| /* RB tree root used to store monitored fd structs */ |
| struct rb_root_cached rbr; |
| |
| /* |
| * This is a single linked list that chains all the "struct epitem" that |
| * happened while transferring ready events to userspace w/out |
| * holding ->lock. |
| */ |
| struct epitem *ovflist; |
| |
| /* wakeup_source used when ep_scan_ready_list is running */ |
| struct wakeup_source *ws; |
| |
| /* The user that created the eventpoll descriptor */ |
| struct user_struct *user; |
| |
| struct file *file; |
| |
| /* used to optimize loop detection check */ |
| u64 gen; |
| struct hlist_head refs; |
| |
| #ifdef CONFIG_NET_RX_BUSY_POLL |
| /* used to track busy poll napi_id */ |
| unsigned int napi_id; |
| #endif |
| |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| /* tracks wakeup nests for lockdep validation */ |
| u8 nests; |
| #endif |
| }; |
| |
| /* Wrapper struct used by poll queueing */ |
| struct ep_pqueue { |
| poll_table pt; |
| struct epitem *epi; |
| }; |
| |
| /* |
| * Configuration options available inside /proc/sys/fs/epoll/ |
| */ |
| /* Maximum number of epoll watched descriptors, per user */ |
| static long max_user_watches __read_mostly; |
| |
| /* |
| * This mutex is used to serialize ep_free() and eventpoll_release_file(). |
| */ |
| static DEFINE_MUTEX(epmutex); |
| |
| static u64 loop_check_gen = 0; |
| |
| /* Used to check for epoll file descriptor inclusion loops */ |
| static struct eventpoll *inserting_into; |
| |
| /* Slab cache used to allocate "struct epitem" */ |
| static struct kmem_cache *epi_cache __read_mostly; |
| |
| /* Slab cache used to allocate "struct eppoll_entry" */ |
| static struct kmem_cache *pwq_cache __read_mostly; |
| |
| /* |
| * List of files with newly added links, where we may need to limit the number |
| * of emanating paths. Protected by the epmutex. |
| */ |
| struct epitems_head { |
| struct hlist_head epitems; |
| struct epitems_head *next; |
| }; |
| static struct epitems_head *tfile_check_list = EP_UNACTIVE_PTR; |
| |
| static struct kmem_cache *ephead_cache __read_mostly; |
| |
| static inline void free_ephead(struct epitems_head *head) |
| { |
| if (head) |
| kmem_cache_free(ephead_cache, head); |
| } |
| |
| static void list_file(struct file *file) |
| { |
| struct epitems_head *head; |
| |
| head = container_of(file->f_ep, struct epitems_head, epitems); |
| if (!head->next) { |
| head->next = tfile_check_list; |
| tfile_check_list = head; |
| } |
| } |
| |
| static void unlist_file(struct epitems_head *head) |
| { |
| struct epitems_head *to_free = head; |
| struct hlist_node *p = rcu_dereference(hlist_first_rcu(&head->epitems)); |
| if (p) { |
| struct epitem *epi= container_of(p, struct epitem, fllink); |
| spin_lock(&epi->ffd.file->f_lock); |
| if (!hlist_empty(&head->epitems)) |
| to_free = NULL; |
| head->next = NULL; |
| spin_unlock(&epi->ffd.file->f_lock); |
| } |
| free_ephead(to_free); |
| } |
| |
| #ifdef CONFIG_SYSCTL |
| |
| #include <linux/sysctl.h> |
| |
| static long long_zero; |
| static long long_max = LONG_MAX; |
| |
| struct ctl_table epoll_table[] = { |
| { |
| .procname = "max_user_watches", |
| .data = &max_user_watches, |
| .maxlen = sizeof(max_user_watches), |
| .mode = 0644, |
| .proc_handler = proc_doulongvec_minmax, |
| .extra1 = &long_zero, |
| .extra2 = &long_max, |
| }, |
| { } |
| }; |
| #endif /* CONFIG_SYSCTL */ |
| |
| static const struct file_operations eventpoll_fops; |
| |
| static inline int is_file_epoll(struct file *f) |
| { |
| return f->f_op == &eventpoll_fops; |
| } |
| |
| /* Setup the structure that is used as key for the RB tree */ |
| static inline void ep_set_ffd(struct epoll_filefd *ffd, |
| struct file *file, int fd) |
| { |
| ffd->file = file; |
| ffd->fd = fd; |
| } |
| |
| /* Compare RB tree keys */ |
| static inline int ep_cmp_ffd(struct epoll_filefd *p1, |
| struct epoll_filefd *p2) |
| { |
| return (p1->file > p2->file ? +1: |
| (p1->file < p2->file ? -1 : p1->fd - p2->fd)); |
| } |
| |
| /* Tells us if the item is currently linked */ |
| static inline int ep_is_linked(struct epitem *epi) |
| { |
| return !list_empty(&epi->rdllink); |
| } |
| |
| static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_entry_t *p) |
| { |
| return container_of(p, struct eppoll_entry, wait); |
| } |
| |
| /* Get the "struct epitem" from a wait queue pointer */ |
| static inline struct epitem *ep_item_from_wait(wait_queue_entry_t *p) |
| { |
| return container_of(p, struct eppoll_entry, wait)->base; |
| } |
| |
| /** |
| * ep_events_available - Checks if ready events might be available. |
| * |
| * @ep: Pointer to the eventpoll context. |
| * |
| * Return: a value different than %zero if ready events are available, |
| * or %zero otherwise. |
| */ |
| static inline int ep_events_available(struct eventpoll *ep) |
| { |
| return !list_empty_careful(&ep->rdllist) || |
| READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR; |
| } |
| |
| #ifdef CONFIG_NET_RX_BUSY_POLL |
| static bool ep_busy_loop_end(void *p, unsigned long start_time) |
| { |
| struct eventpoll *ep = p; |
| |
| return ep_events_available(ep) || busy_loop_timeout(start_time); |
| } |
| |
| /* |
| * Busy poll if globally on and supporting sockets found && no events, |
| * busy loop will return if need_resched or ep_events_available. |
| * |
| * we must do our busy polling with irqs enabled |
| */ |
| static bool ep_busy_loop(struct eventpoll *ep, int nonblock) |
| { |
| unsigned int napi_id = READ_ONCE(ep->napi_id); |
| |
| if ((napi_id >= MIN_NAPI_ID) && net_busy_loop_on()) { |
| napi_busy_loop(napi_id, nonblock ? NULL : ep_busy_loop_end, ep, false, |
| BUSY_POLL_BUDGET); |
| if (ep_events_available(ep)) |
| return true; |
| /* |
| * Busy poll timed out. Drop NAPI ID for now, we can add |
| * it back in when we have moved a socket with a valid NAPI |
| * ID onto the ready list. |
| */ |
| ep->napi_id = 0; |
| return false; |
| } |
| return false; |
| } |
| |
| /* |
| * Set epoll busy poll NAPI ID from sk. |
| */ |
| static inline void ep_set_busy_poll_napi_id(struct epitem *epi) |
| { |
| struct eventpoll *ep; |
| unsigned int napi_id; |
| struct socket *sock; |
| struct sock *sk; |
| |
| if (!net_busy_loop_on()) |
| return; |
| |
| sock = sock_from_file(epi->ffd.file); |
| if (!sock) |
| return; |
| |
| sk = sock->sk; |
| if (!sk) |
| return; |
| |
| napi_id = READ_ONCE(sk->sk_napi_id); |
| ep = epi->ep; |
| |
| /* Non-NAPI IDs can be rejected |
| * or |
| * Nothing to do if we already have this ID |
| */ |
| if (napi_id < MIN_NAPI_ID || napi_id == ep->napi_id) |
| return; |
| |
| /* record NAPI ID for use in next busy poll */ |
| ep->napi_id = napi_id; |
| } |
| |
| #else |
| |
| static inline bool ep_busy_loop(struct eventpoll *ep, int nonblock) |
| { |
| return false; |
| } |
| |
| static inline void ep_set_busy_poll_napi_id(struct epitem *epi) |
| { |
| } |
| |
| #endif /* CONFIG_NET_RX_BUSY_POLL */ |
| |
| /* |
| * As described in commit 0ccf831cb lockdep: annotate epoll |
| * the use of wait queues used by epoll is done in a very controlled |
| * manner. Wake ups can nest inside each other, but are never done |
| * with the same locking. For example: |
| * |
| * dfd = socket(...); |
| * efd1 = epoll_create(); |
| * efd2 = epoll_create(); |
| * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...); |
| * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...); |
| * |
| * When a packet arrives to the device underneath "dfd", the net code will |
| * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a |
| * callback wakeup entry on that queue, and the wake_up() performed by the |
| * "dfd" net code will end up in ep_poll_callback(). At this point epoll |
| * (efd1) notices that it may have some event ready, so it needs to wake up |
| * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake() |
| * that ends up in another wake_up(), after having checked about the |
| * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to |
| * avoid stack blasting. |
| * |
| * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle |
| * this special case of epoll. |
| */ |
| #ifdef CONFIG_DEBUG_LOCK_ALLOC |
| |
| static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi, |
| unsigned pollflags) |
| { |
| struct eventpoll *ep_src; |
| unsigned long flags; |
| u8 nests = 0; |
| |
| /* |
| * To set the subclass or nesting level for spin_lock_irqsave_nested() |
| * it might be natural to create a per-cpu nest count. However, since |
| * we can recurse on ep->poll_wait.lock, and a non-raw spinlock can |
| * schedule() in the -rt kernel, the per-cpu variable are no longer |
| * protected. Thus, we are introducing a per eventpoll nest field. |
| * If we are not being call from ep_poll_callback(), epi is NULL and |
| * we are at the first level of nesting, 0. Otherwise, we are being |
| * called from ep_poll_callback() and if a previous wakeup source is |
| * not an epoll file itself, we are at depth 1 since the wakeup source |
| * is depth 0. If the wakeup source is a previous epoll file in the |
| * wakeup chain then we use its nests value and record ours as |
| * nests + 1. The previous epoll file nests value is stable since its |
| * already holding its own poll_wait.lock. |
| */ |
| if (epi) { |
| if ((is_file_epoll(epi->ffd.file))) { |
| ep_src = epi->ffd.file->private_data; |
| nests = ep_src->nests; |
| } else { |
| nests = 1; |
| } |
| } |
| spin_lock_irqsave_nested(&ep->poll_wait.lock, flags, nests); |
| ep->nests = nests + 1; |
| wake_up_locked_poll(&ep->poll_wait, EPOLLIN | pollflags); |
| ep->nests = 0; |
| spin_unlock_irqrestore(&ep->poll_wait.lock, flags); |
| } |
| |
| #else |
| |
| static void ep_poll_safewake(struct eventpoll *ep, struct epitem *epi, |
| unsigned pollflags) |
| { |
| wake_up_poll(&ep->poll_wait, EPOLLIN | pollflags); |
| } |
| |
| #endif |
| |
| static void ep_remove_wait_queue(struct eppoll_entry *pwq) |
| { |
| wait_queue_head_t *whead; |
| |
| rcu_read_lock(); |
| /* |
| * If it is cleared by POLLFREE, it should be rcu-safe. |
| * If we read NULL we need a barrier paired with |
| * smp_store_release() in ep_poll_callback(), otherwise |
| * we rely on whead->lock. |
| */ |
| whead = smp_load_acquire(&pwq->whead); |
| if (whead) |
| remove_wait_queue(whead, &pwq->wait); |
| rcu_read_unlock(); |
| } |
| |
| /* |
| * This function unregisters poll callbacks from the associated file |
| * descriptor. Must be called with "mtx" held (or "epmutex" if called from |
| * ep_free). |
| */ |
| static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi) |
| { |
| struct eppoll_entry **p = &epi->pwqlist; |
| struct eppoll_entry *pwq; |
| |
| while ((pwq = *p) != NULL) { |
| *p = pwq->next; |
| ep_remove_wait_queue(pwq); |
| kmem_cache_free(pwq_cache, pwq); |
| } |
| } |
| |
| /* call only when ep->mtx is held */ |
| static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi) |
| { |
| return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx)); |
| } |
| |
| /* call only when ep->mtx is held */ |
| static inline void ep_pm_stay_awake(struct epitem *epi) |
| { |
| struct wakeup_source *ws = ep_wakeup_source(epi); |
| |
| if (ws) |
| __pm_stay_awake(ws); |
| } |
| |
| static inline bool ep_has_wakeup_source(struct epitem *epi) |
| { |
| return rcu_access_pointer(epi->ws) ? true : false; |
| } |
| |
| /* call when ep->mtx cannot be held (ep_poll_callback) */ |
| static inline void ep_pm_stay_awake_rcu(struct epitem *epi) |
| { |
| struct wakeup_source *ws; |
| |
| rcu_read_lock(); |
| ws = rcu_dereference(epi->ws); |
| if (ws) |
| __pm_stay_awake(ws); |
| rcu_read_unlock(); |
| } |
| |
| |
| /* |
| * ep->mutex needs to be held because we could be hit by |
| * eventpoll_release_file() and epoll_ctl(). |
| */ |
| static void ep_start_scan(struct eventpoll *ep, struct list_head *txlist) |
| { |
| /* |
| * Steal the ready list, and re-init the original one to the |
| * empty list. Also, set ep->ovflist to NULL so that events |
| * happening while looping w/out locks, are not lost. We cannot |
| * have the poll callback to queue directly on ep->rdllist, |
| * because we want the "sproc" callback to be able to do it |
| * in a lockless way. |
| */ |
| lockdep_assert_irqs_enabled(); |
| write_lock_irq(&ep->lock); |
| list_splice_init(&ep->rdllist, txlist); |
| WRITE_ONCE(ep->ovflist, NULL); |
| write_unlock_irq(&ep->lock); |
| } |
| |
| static void ep_done_scan(struct eventpoll *ep, |
| struct list_head *txlist) |
| { |
| struct epitem *epi, *nepi; |
| |
| write_lock_irq(&ep->lock); |
| /* |
| * During the time we spent inside the "sproc" callback, some |
| * other events might have been queued by the poll callback. |
| * We re-insert them inside the main ready-list here. |
| */ |
| for (nepi = READ_ONCE(ep->ovflist); (epi = nepi) != NULL; |
| nepi = epi->next, epi->next = EP_UNACTIVE_PTR) { |
| /* |
| * We need to check if the item is already in the list. |
| * During the "sproc" callback execution time, items are |
| * queued into ->ovflist but the "txlist" might already |
| * contain them, and the list_splice() below takes care of them. |
| */ |
| if (!ep_is_linked(epi)) { |
| /* |
| * ->ovflist is LIFO, so we have to reverse it in order |
| * to keep in FIFO. |
| */ |
| list_add(&epi->rdllink, &ep->rdllist); |
| ep_pm_stay_awake(epi); |
| } |
| } |
| /* |
| * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after |
| * releasing the lock, events will be queued in the normal way inside |
| * ep->rdllist. |
| */ |
| WRITE_ONCE(ep->ovflist, EP_UNACTIVE_PTR); |
| |
| /* |
| * Quickly re-inject items left on "txlist". |
| */ |
| list_splice(txlist, &ep->rdllist); |
| __pm_relax(ep->ws); |
| |
| if (!list_empty(&ep->rdllist)) { |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| } |
| |
| write_unlock_irq(&ep->lock); |
| } |
| |
| static void epi_rcu_free(struct rcu_head *head) |
| { |
| struct epitem *epi = container_of(head, struct epitem, rcu); |
| kmem_cache_free(epi_cache, epi); |
| } |
| |
| /* |
| * Removes a "struct epitem" from the eventpoll RB tree and deallocates |
| * all the associated resources. Must be called with "mtx" held. |
| */ |
| static int ep_remove(struct eventpoll *ep, struct epitem *epi) |
| { |
| struct file *file = epi->ffd.file; |
| struct epitems_head *to_free; |
| struct hlist_head *head; |
| |
| lockdep_assert_irqs_enabled(); |
| |
| /* |
| * Removes poll wait queue hooks. |
| */ |
| ep_unregister_pollwait(ep, epi); |
| |
| /* Remove the current item from the list of epoll hooks */ |
| spin_lock(&file->f_lock); |
| to_free = NULL; |
| head = file->f_ep; |
| if (head->first == &epi->fllink && !epi->fllink.next) { |
| file->f_ep = NULL; |
| if (!is_file_epoll(file)) { |
| struct epitems_head *v; |
| v = container_of(head, struct epitems_head, epitems); |
| if (!smp_load_acquire(&v->next)) |
| to_free = v; |
| } |
| } |
| hlist_del_rcu(&epi->fllink); |
| spin_unlock(&file->f_lock); |
| free_ephead(to_free); |
| |
| rb_erase_cached(&epi->rbn, &ep->rbr); |
| |
| write_lock_irq(&ep->lock); |
| if (ep_is_linked(epi)) |
| list_del_init(&epi->rdllink); |
| write_unlock_irq(&ep->lock); |
| |
| wakeup_source_unregister(ep_wakeup_source(epi)); |
| /* |
| * At this point it is safe to free the eventpoll item. Use the union |
| * field epi->rcu, since we are trying to minimize the size of |
| * 'struct epitem'. The 'rbn' field is no longer in use. Protected by |
| * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make |
| * use of the rbn field. |
| */ |
| call_rcu(&epi->rcu, epi_rcu_free); |
| |
| percpu_counter_dec(&ep->user->epoll_watches); |
| |
| return 0; |
| } |
| |
| static void ep_free(struct eventpoll *ep) |
| { |
| struct rb_node *rbp; |
| struct epitem *epi; |
| |
| /* We need to release all tasks waiting for these file */ |
| if (waitqueue_active(&ep->poll_wait)) |
| ep_poll_safewake(ep, NULL, 0); |
| |
| /* |
| * We need to lock this because we could be hit by |
| * eventpoll_release_file() while we're freeing the "struct eventpoll". |
| * We do not need to hold "ep->mtx" here because the epoll file |
| * is on the way to be removed and no one has references to it |
| * anymore. The only hit might come from eventpoll_release_file() but |
| * holding "epmutex" is sufficient here. |
| */ |
| mutex_lock(&epmutex); |
| |
| /* |
| * Walks through the whole tree by unregistering poll callbacks. |
| */ |
| for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
| epi = rb_entry(rbp, struct epitem, rbn); |
| |
| ep_unregister_pollwait(ep, epi); |
| cond_resched(); |
| } |
| |
| /* |
| * Walks through the whole tree by freeing each "struct epitem". At this |
| * point we are sure no poll callbacks will be lingering around, and also by |
| * holding "epmutex" we can be sure that no file cleanup code will hit |
| * us during this operation. So we can avoid the lock on "ep->lock". |
| * We do not need to lock ep->mtx, either, we only do it to prevent |
| * a lockdep warning. |
| */ |
| mutex_lock(&ep->mtx); |
| while ((rbp = rb_first_cached(&ep->rbr)) != NULL) { |
| epi = rb_entry(rbp, struct epitem, rbn); |
| ep_remove(ep, epi); |
| cond_resched(); |
| } |
| mutex_unlock(&ep->mtx); |
| |
| mutex_unlock(&epmutex); |
| mutex_destroy(&ep->mtx); |
| free_uid(ep->user); |
| wakeup_source_unregister(ep->ws); |
| kfree(ep); |
| } |
| |
| static int ep_eventpoll_release(struct inode *inode, struct file *file) |
| { |
| struct eventpoll *ep = file->private_data; |
| |
| if (ep) |
| ep_free(ep); |
| |
| return 0; |
| } |
| |
| static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt, int depth); |
| |
| static __poll_t __ep_eventpoll_poll(struct file *file, poll_table *wait, int depth) |
| { |
| struct eventpoll *ep = file->private_data; |
| LIST_HEAD(txlist); |
| struct epitem *epi, *tmp; |
| poll_table pt; |
| __poll_t res = 0; |
| |
| init_poll_funcptr(&pt, NULL); |
| |
| /* Insert inside our poll wait queue */ |
| poll_wait(file, &ep->poll_wait, wait); |
| |
| /* |
| * Proceed to find out if wanted events are really available inside |
| * the ready list. |
| */ |
| mutex_lock_nested(&ep->mtx, depth); |
| ep_start_scan(ep, &txlist); |
| list_for_each_entry_safe(epi, tmp, &txlist, rdllink) { |
| if (ep_item_poll(epi, &pt, depth + 1)) { |
| res = EPOLLIN | EPOLLRDNORM; |
| break; |
| } else { |
| /* |
| * Item has been dropped into the ready list by the poll |
| * callback, but it's not actually ready, as far as |
| * caller requested events goes. We can remove it here. |
| */ |
| __pm_relax(ep_wakeup_source(epi)); |
| list_del_init(&epi->rdllink); |
| } |
| } |
| ep_done_scan(ep, &txlist); |
| mutex_unlock(&ep->mtx); |
| return res; |
| } |
| |
| /* |
| * The ffd.file pointer may be in the process of being torn down due to |
| * being closed, but we may not have finished eventpoll_release() yet. |
| * |
| * Normally, even with the atomic_long_inc_not_zero, the file may have |
| * been free'd and then gotten re-allocated to something else (since |
| * files are not RCU-delayed, they are SLAB_TYPESAFE_BY_RCU). |
| * |
| * But for epoll, users hold the ep->mtx mutex, and as such any file in |
| * the process of being free'd will block in eventpoll_release_file() |
| * and thus the underlying file allocation will not be free'd, and the |
| * file re-use cannot happen. |
| * |
| * For the same reason we can avoid a rcu_read_lock() around the |
| * operation - 'ffd.file' cannot go away even if the refcount has |
| * reached zero (but we must still not call out to ->poll() functions |
| * etc). |
| */ |
| static struct file *epi_fget(const struct epitem *epi) |
| { |
| struct file *file; |
| |
| file = epi->ffd.file; |
| if (!atomic_long_inc_not_zero(&file->f_count)) |
| file = NULL; |
| return file; |
| } |
| |
| /* |
| * Differs from ep_eventpoll_poll() in that internal callers already have |
| * the ep->mtx so we need to start from depth=1, such that mutex_lock_nested() |
| * is correctly annotated. |
| */ |
| static __poll_t ep_item_poll(const struct epitem *epi, poll_table *pt, |
| int depth) |
| { |
| struct file *file = epi_fget(epi); |
| __poll_t res; |
| |
| /* |
| * We could return EPOLLERR | EPOLLHUP or something, but let's |
| * treat this more as "file doesn't exist, poll didn't happen". |
| */ |
| if (!file) |
| return 0; |
| |
| pt->_key = epi->event.events; |
| if (!is_file_epoll(file)) |
| res = vfs_poll(file, pt); |
| else |
| res = __ep_eventpoll_poll(file, pt, depth); |
| fput(file); |
| return res & epi->event.events; |
| } |
| |
| static __poll_t ep_eventpoll_poll(struct file *file, poll_table *wait) |
| { |
| return __ep_eventpoll_poll(file, wait, 0); |
| } |
| |
| #ifdef CONFIG_PROC_FS |
| static void ep_show_fdinfo(struct seq_file *m, struct file *f) |
| { |
| struct eventpoll *ep = f->private_data; |
| struct rb_node *rbp; |
| |
| mutex_lock(&ep->mtx); |
| for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
| struct epitem *epi = rb_entry(rbp, struct epitem, rbn); |
| struct inode *inode = file_inode(epi->ffd.file); |
| |
| seq_printf(m, "tfd: %8d events: %8x data: %16llx " |
| " pos:%lli ino:%lx sdev:%x\n", |
| epi->ffd.fd, epi->event.events, |
| (long long)epi->event.data, |
| (long long)epi->ffd.file->f_pos, |
| inode->i_ino, inode->i_sb->s_dev); |
| if (seq_has_overflowed(m)) |
| break; |
| } |
| mutex_unlock(&ep->mtx); |
| } |
| #endif |
| |
| /* File callbacks that implement the eventpoll file behaviour */ |
| static const struct file_operations eventpoll_fops = { |
| #ifdef CONFIG_PROC_FS |
| .show_fdinfo = ep_show_fdinfo, |
| #endif |
| .release = ep_eventpoll_release, |
| .poll = ep_eventpoll_poll, |
| .llseek = noop_llseek, |
| }; |
| |
| /* |
| * This is called from eventpoll_release() to unlink files from the eventpoll |
| * interface. We need to have this facility to cleanup correctly files that are |
| * closed without being removed from the eventpoll interface. |
| */ |
| void eventpoll_release_file(struct file *file) |
| { |
| struct eventpoll *ep; |
| struct epitem *epi; |
| struct hlist_node *next; |
| |
| /* |
| * We don't want to get "file->f_lock" because it is not |
| * necessary. It is not necessary because we're in the "struct file" |
| * cleanup path, and this means that no one is using this file anymore. |
| * So, for example, epoll_ctl() cannot hit here since if we reach this |
| * point, the file counter already went to zero and fget() would fail. |
| * The only hit might come from ep_free() but by holding the mutex |
| * will correctly serialize the operation. We do need to acquire |
| * "ep->mtx" after "epmutex" because ep_remove() requires it when called |
| * from anywhere but ep_free(). |
| * |
| * Besides, ep_remove() acquires the lock, so we can't hold it here. |
| */ |
| mutex_lock(&epmutex); |
| if (unlikely(!file->f_ep)) { |
| mutex_unlock(&epmutex); |
| return; |
| } |
| hlist_for_each_entry_safe(epi, next, file->f_ep, fllink) { |
| ep = epi->ep; |
| mutex_lock_nested(&ep->mtx, 0); |
| ep_remove(ep, epi); |
| mutex_unlock(&ep->mtx); |
| } |
| mutex_unlock(&epmutex); |
| } |
| |
| static int ep_alloc(struct eventpoll **pep) |
| { |
| int error; |
| struct user_struct *user; |
| struct eventpoll *ep; |
| |
| user = get_current_user(); |
| error = -ENOMEM; |
| ep = kzalloc(sizeof(*ep), GFP_KERNEL); |
| if (unlikely(!ep)) |
| goto free_uid; |
| |
| mutex_init(&ep->mtx); |
| rwlock_init(&ep->lock); |
| init_waitqueue_head(&ep->wq); |
| init_waitqueue_head(&ep->poll_wait); |
| INIT_LIST_HEAD(&ep->rdllist); |
| ep->rbr = RB_ROOT_CACHED; |
| ep->ovflist = EP_UNACTIVE_PTR; |
| ep->user = user; |
| |
| *pep = ep; |
| |
| return 0; |
| |
| free_uid: |
| free_uid(user); |
| return error; |
| } |
| |
| /* |
| * Search the file inside the eventpoll tree. The RB tree operations |
| * are protected by the "mtx" mutex, and ep_find() must be called with |
| * "mtx" held. |
| */ |
| static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd) |
| { |
| int kcmp; |
| struct rb_node *rbp; |
| struct epitem *epi, *epir = NULL; |
| struct epoll_filefd ffd; |
| |
| ep_set_ffd(&ffd, file, fd); |
| for (rbp = ep->rbr.rb_root.rb_node; rbp; ) { |
| epi = rb_entry(rbp, struct epitem, rbn); |
| kcmp = ep_cmp_ffd(&ffd, &epi->ffd); |
| if (kcmp > 0) |
| rbp = rbp->rb_right; |
| else if (kcmp < 0) |
| rbp = rbp->rb_left; |
| else { |
| epir = epi; |
| break; |
| } |
| } |
| |
| return epir; |
| } |
| |
| #ifdef CONFIG_KCMP |
| static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff) |
| { |
| struct rb_node *rbp; |
| struct epitem *epi; |
| |
| for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
| epi = rb_entry(rbp, struct epitem, rbn); |
| if (epi->ffd.fd == tfd) { |
| if (toff == 0) |
| return epi; |
| else |
| toff--; |
| } |
| cond_resched(); |
| } |
| |
| return NULL; |
| } |
| |
| struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, |
| unsigned long toff) |
| { |
| struct file *file_raw; |
| struct eventpoll *ep; |
| struct epitem *epi; |
| |
| if (!is_file_epoll(file)) |
| return ERR_PTR(-EINVAL); |
| |
| ep = file->private_data; |
| |
| mutex_lock(&ep->mtx); |
| epi = ep_find_tfd(ep, tfd, toff); |
| if (epi) |
| file_raw = epi->ffd.file; |
| else |
| file_raw = ERR_PTR(-ENOENT); |
| mutex_unlock(&ep->mtx); |
| |
| return file_raw; |
| } |
| #endif /* CONFIG_KCMP */ |
| |
| /* |
| * Adds a new entry to the tail of the list in a lockless way, i.e. |
| * multiple CPUs are allowed to call this function concurrently. |
| * |
| * Beware: it is necessary to prevent any other modifications of the |
| * existing list until all changes are completed, in other words |
| * concurrent list_add_tail_lockless() calls should be protected |
| * with a read lock, where write lock acts as a barrier which |
| * makes sure all list_add_tail_lockless() calls are fully |
| * completed. |
| * |
| * Also an element can be locklessly added to the list only in one |
| * direction i.e. either to the tail or to the head, otherwise |
| * concurrent access will corrupt the list. |
| * |
| * Return: %false if element has been already added to the list, %true |
| * otherwise. |
| */ |
| static inline bool list_add_tail_lockless(struct list_head *new, |
| struct list_head *head) |
| { |
| struct list_head *prev; |
| |
| /* |
| * This is simple 'new->next = head' operation, but cmpxchg() |
| * is used in order to detect that same element has been just |
| * added to the list from another CPU: the winner observes |
| * new->next == new. |
| */ |
| if (cmpxchg(&new->next, new, head) != new) |
| return false; |
| |
| /* |
| * Initially ->next of a new element must be updated with the head |
| * (we are inserting to the tail) and only then pointers are atomically |
| * exchanged. XCHG guarantees memory ordering, thus ->next should be |
| * updated before pointers are actually swapped and pointers are |
| * swapped before prev->next is updated. |
| */ |
| |
| prev = xchg(&head->prev, new); |
| |
| /* |
| * It is safe to modify prev->next and new->prev, because a new element |
| * is added only to the tail and new->next is updated before XCHG. |
| */ |
| |
| prev->next = new; |
| new->prev = prev; |
| |
| return true; |
| } |
| |
| /* |
| * Chains a new epi entry to the tail of the ep->ovflist in a lockless way, |
| * i.e. multiple CPUs are allowed to call this function concurrently. |
| * |
| * Return: %false if epi element has been already chained, %true otherwise. |
| */ |
| static inline bool chain_epi_lockless(struct epitem *epi) |
| { |
| struct eventpoll *ep = epi->ep; |
| |
| /* Fast preliminary check */ |
| if (epi->next != EP_UNACTIVE_PTR) |
| return false; |
| |
| /* Check that the same epi has not been just chained from another CPU */ |
| if (cmpxchg(&epi->next, EP_UNACTIVE_PTR, NULL) != EP_UNACTIVE_PTR) |
| return false; |
| |
| /* Atomically exchange tail */ |
| epi->next = xchg(&ep->ovflist, epi); |
| |
| return true; |
| } |
| |
| /* |
| * This is the callback that is passed to the wait queue wakeup |
| * mechanism. It is called by the stored file descriptors when they |
| * have events to report. |
| * |
| * This callback takes a read lock in order not to contend with concurrent |
| * events from another file descriptor, thus all modifications to ->rdllist |
| * or ->ovflist are lockless. Read lock is paired with the write lock from |
| * ep_scan_ready_list(), which stops all list modifications and guarantees |
| * that lists state is seen correctly. |
| * |
| * Another thing worth to mention is that ep_poll_callback() can be called |
| * concurrently for the same @epi from different CPUs if poll table was inited |
| * with several wait queues entries. Plural wakeup from different CPUs of a |
| * single wait queue is serialized by wq.lock, but the case when multiple wait |
| * queues are used should be detected accordingly. This is detected using |
| * cmpxchg() operation. |
| */ |
| static int ep_poll_callback(wait_queue_entry_t *wait, unsigned mode, int sync, void *key) |
| { |
| int pwake = 0; |
| struct epitem *epi = ep_item_from_wait(wait); |
| struct eventpoll *ep = epi->ep; |
| __poll_t pollflags = key_to_poll(key); |
| unsigned long flags; |
| int ewake = 0; |
| |
| read_lock_irqsave(&ep->lock, flags); |
| |
| ep_set_busy_poll_napi_id(epi); |
| |
| /* |
| * If the event mask does not contain any poll(2) event, we consider the |
| * descriptor to be disabled. This condition is likely the effect of the |
| * EPOLLONESHOT bit that disables the descriptor when an event is received, |
| * until the next EPOLL_CTL_MOD will be issued. |
| */ |
| if (!(epi->event.events & ~EP_PRIVATE_BITS)) |
| goto out_unlock; |
| |
| /* |
| * Check the events coming with the callback. At this stage, not |
| * every device reports the events in the "key" parameter of the |
| * callback. We need to be able to handle both cases here, hence the |
| * test for "key" != NULL before the event match test. |
| */ |
| if (pollflags && !(pollflags & epi->event.events)) |
| goto out_unlock; |
| |
| /* |
| * If we are transferring events to userspace, we can hold no locks |
| * (because we're accessing user memory, and because of linux f_op->poll() |
| * semantics). All the events that happen during that period of time are |
| * chained in ep->ovflist and requeued later on. |
| */ |
| if (READ_ONCE(ep->ovflist) != EP_UNACTIVE_PTR) { |
| if (chain_epi_lockless(epi)) |
| ep_pm_stay_awake_rcu(epi); |
| } else if (!ep_is_linked(epi)) { |
| /* In the usual case, add event to ready list. */ |
| if (list_add_tail_lockless(&epi->rdllink, &ep->rdllist)) |
| ep_pm_stay_awake_rcu(epi); |
| } |
| |
| /* |
| * Wake up ( if active ) both the eventpoll wait list and the ->poll() |
| * wait list. |
| */ |
| if (waitqueue_active(&ep->wq)) { |
| if ((epi->event.events & EPOLLEXCLUSIVE) && |
| !(pollflags & POLLFREE)) { |
| switch (pollflags & EPOLLINOUT_BITS) { |
| case EPOLLIN: |
| if (epi->event.events & EPOLLIN) |
| ewake = 1; |
| break; |
| case EPOLLOUT: |
| if (epi->event.events & EPOLLOUT) |
| ewake = 1; |
| break; |
| case 0: |
| ewake = 1; |
| break; |
| } |
| } |
| wake_up(&ep->wq); |
| } |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| |
| out_unlock: |
| read_unlock_irqrestore(&ep->lock, flags); |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(ep, epi, pollflags & EPOLL_URING_WAKE); |
| |
| if (!(epi->event.events & EPOLLEXCLUSIVE)) |
| ewake = 1; |
| |
| if (pollflags & POLLFREE) { |
| /* |
| * If we race with ep_remove_wait_queue() it can miss |
| * ->whead = NULL and do another remove_wait_queue() after |
| * us, so we can't use __remove_wait_queue(). |
| */ |
| list_del_init(&wait->entry); |
| /* |
| * ->whead != NULL protects us from the race with ep_free() |
| * or ep_remove(), ep_remove_wait_queue() takes whead->lock |
| * held by the caller. Once we nullify it, nothing protects |
| * ep/epi or even wait. |
| */ |
| smp_store_release(&ep_pwq_from_wait(wait)->whead, NULL); |
| } |
| |
| return ewake; |
| } |
| |
| /* |
| * This is the callback that is used to add our wait queue to the |
| * target file wakeup lists. |
| */ |
| static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead, |
| poll_table *pt) |
| { |
| struct ep_pqueue *epq = container_of(pt, struct ep_pqueue, pt); |
| struct epitem *epi = epq->epi; |
| struct eppoll_entry *pwq; |
| |
| if (unlikely(!epi)) // an earlier allocation has failed |
| return; |
| |
| pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL); |
| if (unlikely(!pwq)) { |
| epq->epi = NULL; |
| return; |
| } |
| |
| init_waitqueue_func_entry(&pwq->wait, ep_poll_callback); |
| pwq->whead = whead; |
| pwq->base = epi; |
| if (epi->event.events & EPOLLEXCLUSIVE) |
| add_wait_queue_exclusive(whead, &pwq->wait); |
| else |
| add_wait_queue(whead, &pwq->wait); |
| pwq->next = epi->pwqlist; |
| epi->pwqlist = pwq; |
| } |
| |
| static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) |
| { |
| int kcmp; |
| struct rb_node **p = &ep->rbr.rb_root.rb_node, *parent = NULL; |
| struct epitem *epic; |
| bool leftmost = true; |
| |
| while (*p) { |
| parent = *p; |
| epic = rb_entry(parent, struct epitem, rbn); |
| kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd); |
| if (kcmp > 0) { |
| p = &parent->rb_right; |
| leftmost = false; |
| } else |
| p = &parent->rb_left; |
| } |
| rb_link_node(&epi->rbn, parent, p); |
| rb_insert_color_cached(&epi->rbn, &ep->rbr, leftmost); |
| } |
| |
| |
| |
| #define PATH_ARR_SIZE 5 |
| /* |
| * These are the number paths of length 1 to 5, that we are allowing to emanate |
| * from a single file of interest. For example, we allow 1000 paths of length |
| * 1, to emanate from each file of interest. This essentially represents the |
| * potential wakeup paths, which need to be limited in order to avoid massive |
| * uncontrolled wakeup storms. The common use case should be a single ep which |
| * is connected to n file sources. In this case each file source has 1 path |
| * of length 1. Thus, the numbers below should be more than sufficient. These |
| * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify |
| * and delete can't add additional paths. Protected by the epmutex. |
| */ |
| static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 }; |
| static int path_count[PATH_ARR_SIZE]; |
| |
| static int path_count_inc(int nests) |
| { |
| /* Allow an arbitrary number of depth 1 paths */ |
| if (nests == 0) |
| return 0; |
| |
| if (++path_count[nests] > path_limits[nests]) |
| return -1; |
| return 0; |
| } |
| |
| static void path_count_init(void) |
| { |
| int i; |
| |
| for (i = 0; i < PATH_ARR_SIZE; i++) |
| path_count[i] = 0; |
| } |
| |
| static int reverse_path_check_proc(struct hlist_head *refs, int depth) |
| { |
| int error = 0; |
| struct epitem *epi; |
| |
| if (depth > EP_MAX_NESTS) /* too deep nesting */ |
| return -1; |
| |
| /* CTL_DEL can remove links here, but that can't increase our count */ |
| hlist_for_each_entry_rcu(epi, refs, fllink) { |
| struct hlist_head *refs = &epi->ep->refs; |
| if (hlist_empty(refs)) |
| error = path_count_inc(depth); |
| else |
| error = reverse_path_check_proc(refs, depth + 1); |
| if (error != 0) |
| break; |
| } |
| return error; |
| } |
| |
| /** |
| * reverse_path_check - The tfile_check_list is list of epitem_head, which have |
| * links that are proposed to be newly added. We need to |
| * make sure that those added links don't add too many |
| * paths such that we will spend all our time waking up |
| * eventpoll objects. |
| * |
| * Return: %zero if the proposed links don't create too many paths, |
| * %-1 otherwise. |
| */ |
| static int reverse_path_check(void) |
| { |
| struct epitems_head *p; |
| |
| for (p = tfile_check_list; p != EP_UNACTIVE_PTR; p = p->next) { |
| int error; |
| path_count_init(); |
| rcu_read_lock(); |
| error = reverse_path_check_proc(&p->epitems, 0); |
| rcu_read_unlock(); |
| if (error) |
| return error; |
| } |
| return 0; |
| } |
| |
| static int ep_create_wakeup_source(struct epitem *epi) |
| { |
| struct name_snapshot n; |
| struct wakeup_source *ws; |
| |
| if (!epi->ep->ws) { |
| epi->ep->ws = wakeup_source_register(NULL, "eventpoll"); |
| if (!epi->ep->ws) |
| return -ENOMEM; |
| } |
| |
| take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry); |
| ws = wakeup_source_register(NULL, n.name.name); |
| release_dentry_name_snapshot(&n); |
| |
| if (!ws) |
| return -ENOMEM; |
| rcu_assign_pointer(epi->ws, ws); |
| |
| return 0; |
| } |
| |
| /* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */ |
| static noinline void ep_destroy_wakeup_source(struct epitem *epi) |
| { |
| struct wakeup_source *ws = ep_wakeup_source(epi); |
| |
| RCU_INIT_POINTER(epi->ws, NULL); |
| |
| /* |
| * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is |
| * used internally by wakeup_source_remove, too (called by |
| * wakeup_source_unregister), so we cannot use call_rcu |
| */ |
| synchronize_rcu(); |
| wakeup_source_unregister(ws); |
| } |
| |
| static int attach_epitem(struct file *file, struct epitem *epi) |
| { |
| struct epitems_head *to_free = NULL; |
| struct hlist_head *head = NULL; |
| struct eventpoll *ep = NULL; |
| |
| if (is_file_epoll(file)) |
| ep = file->private_data; |
| |
| if (ep) { |
| head = &ep->refs; |
| } else if (!READ_ONCE(file->f_ep)) { |
| allocate: |
| to_free = kmem_cache_zalloc(ephead_cache, GFP_KERNEL); |
| if (!to_free) |
| return -ENOMEM; |
| head = &to_free->epitems; |
| } |
| spin_lock(&file->f_lock); |
| if (!file->f_ep) { |
| if (unlikely(!head)) { |
| spin_unlock(&file->f_lock); |
| goto allocate; |
| } |
| file->f_ep = head; |
| to_free = NULL; |
| } |
| hlist_add_head_rcu(&epi->fllink, file->f_ep); |
| spin_unlock(&file->f_lock); |
| free_ephead(to_free); |
| return 0; |
| } |
| |
| /* |
| * Must be called with "mtx" held. |
| */ |
| static int ep_insert(struct eventpoll *ep, const struct epoll_event *event, |
| struct file *tfile, int fd, int full_check) |
| { |
| int error, pwake = 0; |
| __poll_t revents; |
| struct epitem *epi; |
| struct ep_pqueue epq; |
| struct eventpoll *tep = NULL; |
| |
| if (is_file_epoll(tfile)) |
| tep = tfile->private_data; |
| |
| lockdep_assert_irqs_enabled(); |
| |
| if (unlikely(percpu_counter_compare(&ep->user->epoll_watches, |
| max_user_watches) >= 0)) |
| return -ENOSPC; |
| percpu_counter_inc(&ep->user->epoll_watches); |
| |
| if (!(epi = kmem_cache_zalloc(epi_cache, GFP_KERNEL))) { |
| percpu_counter_dec(&ep->user->epoll_watches); |
| return -ENOMEM; |
| } |
| |
| /* Item initialization follow here ... */ |
| INIT_LIST_HEAD(&epi->rdllink); |
| epi->ep = ep; |
| ep_set_ffd(&epi->ffd, tfile, fd); |
| epi->event = *event; |
| epi->next = EP_UNACTIVE_PTR; |
| |
| if (tep) |
| mutex_lock_nested(&tep->mtx, 1); |
| /* Add the current item to the list of active epoll hook for this file */ |
| if (unlikely(attach_epitem(tfile, epi) < 0)) { |
| if (tep) |
| mutex_unlock(&tep->mtx); |
| kmem_cache_free(epi_cache, epi); |
| percpu_counter_dec(&ep->user->epoll_watches); |
| return -ENOMEM; |
| } |
| |
| if (full_check && !tep) |
| list_file(tfile); |
| |
| /* |
| * Add the current item to the RB tree. All RB tree operations are |
| * protected by "mtx", and ep_insert() is called with "mtx" held. |
| */ |
| ep_rbtree_insert(ep, epi); |
| if (tep) |
| mutex_unlock(&tep->mtx); |
| |
| /* now check if we've created too many backpaths */ |
| if (unlikely(full_check && reverse_path_check())) { |
| ep_remove(ep, epi); |
| return -EINVAL; |
| } |
| |
| if (epi->event.events & EPOLLWAKEUP) { |
| error = ep_create_wakeup_source(epi); |
| if (error) { |
| ep_remove(ep, epi); |
| return error; |
| } |
| } |
| |
| /* Initialize the poll table using the queue callback */ |
| epq.epi = epi; |
| init_poll_funcptr(&epq.pt, ep_ptable_queue_proc); |
| |
| /* |
| * Attach the item to the poll hooks and get current event bits. |
| * We can safely use the file* here because its usage count has |
| * been increased by the caller of this function. Note that after |
| * this operation completes, the poll callback can start hitting |
| * the new item. |
| */ |
| revents = ep_item_poll(epi, &epq.pt, 1); |
| |
| /* |
| * We have to check if something went wrong during the poll wait queue |
| * install process. Namely an allocation for a wait queue failed due |
| * high memory pressure. |
| */ |
| if (unlikely(!epq.epi)) { |
| ep_remove(ep, epi); |
| return -ENOMEM; |
| } |
| |
| /* We have to drop the new item inside our item list to keep track of it */ |
| write_lock_irq(&ep->lock); |
| |
| /* record NAPI ID of new item if present */ |
| ep_set_busy_poll_napi_id(epi); |
| |
| /* If the file is already "ready" we drop it inside the ready list */ |
| if (revents && !ep_is_linked(epi)) { |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| ep_pm_stay_awake(epi); |
| |
| /* Notify waiting tasks that events are available */ |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| } |
| |
| write_unlock_irq(&ep->lock); |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(ep, NULL, 0); |
| |
| return 0; |
| } |
| |
| /* |
| * Modify the interest event mask by dropping an event if the new mask |
| * has a match in the current file status. Must be called with "mtx" held. |
| */ |
| static int ep_modify(struct eventpoll *ep, struct epitem *epi, |
| const struct epoll_event *event) |
| { |
| int pwake = 0; |
| poll_table pt; |
| |
| lockdep_assert_irqs_enabled(); |
| |
| init_poll_funcptr(&pt, NULL); |
| |
| /* |
| * Set the new event interest mask before calling f_op->poll(); |
| * otherwise we might miss an event that happens between the |
| * f_op->poll() call and the new event set registering. |
| */ |
| epi->event.events = event->events; /* need barrier below */ |
| epi->event.data = event->data; /* protected by mtx */ |
| if (epi->event.events & EPOLLWAKEUP) { |
| if (!ep_has_wakeup_source(epi)) |
| ep_create_wakeup_source(epi); |
| } else if (ep_has_wakeup_source(epi)) { |
| ep_destroy_wakeup_source(epi); |
| } |
| |
| /* |
| * The following barrier has two effects: |
| * |
| * 1) Flush epi changes above to other CPUs. This ensures |
| * we do not miss events from ep_poll_callback if an |
| * event occurs immediately after we call f_op->poll(). |
| * We need this because we did not take ep->lock while |
| * changing epi above (but ep_poll_callback does take |
| * ep->lock). |
| * |
| * 2) We also need to ensure we do not miss _past_ events |
| * when calling f_op->poll(). This barrier also |
| * pairs with the barrier in wq_has_sleeper (see |
| * comments for wq_has_sleeper). |
| * |
| * This barrier will now guarantee ep_poll_callback or f_op->poll |
| * (or both) will notice the readiness of an item. |
| */ |
| smp_mb(); |
| |
| /* |
| * Get current event bits. We can safely use the file* here because |
| * its usage count has been increased by the caller of this function. |
| * If the item is "hot" and it is not registered inside the ready |
| * list, push it inside. |
| */ |
| if (ep_item_poll(epi, &pt, 1)) { |
| write_lock_irq(&ep->lock); |
| if (!ep_is_linked(epi)) { |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| ep_pm_stay_awake(epi); |
| |
| /* Notify waiting tasks that events are available */ |
| if (waitqueue_active(&ep->wq)) |
| wake_up(&ep->wq); |
| if (waitqueue_active(&ep->poll_wait)) |
| pwake++; |
| } |
| write_unlock_irq(&ep->lock); |
| } |
| |
| /* We have to call this outside the lock */ |
| if (pwake) |
| ep_poll_safewake(ep, NULL, 0); |
| |
| return 0; |
| } |
| |
| static int ep_send_events(struct eventpoll *ep, |
| struct epoll_event __user *events, int maxevents) |
| { |
| struct epitem *epi, *tmp; |
| LIST_HEAD(txlist); |
| poll_table pt; |
| int res = 0; |
| |
| /* |
| * Always short-circuit for fatal signals to allow threads to make a |
| * timely exit without the chance of finding more events available and |
| * fetching repeatedly. |
| */ |
| if (fatal_signal_pending(current)) |
| return -EINTR; |
| |
| init_poll_funcptr(&pt, NULL); |
| |
| mutex_lock(&ep->mtx); |
| ep_start_scan(ep, &txlist); |
| |
| /* |
| * We can loop without lock because we are passed a task private list. |
| * Items cannot vanish during the loop we are holding ep->mtx. |
| */ |
| list_for_each_entry_safe(epi, tmp, &txlist, rdllink) { |
| struct wakeup_source *ws; |
| __poll_t revents; |
| |
| if (res >= maxevents) |
| break; |
| |
| /* |
| * Activate ep->ws before deactivating epi->ws to prevent |
| * triggering auto-suspend here (in case we reactive epi->ws |
| * below). |
| * |
| * This could be rearranged to delay the deactivation of epi->ws |
| * instead, but then epi->ws would temporarily be out of sync |
| * with ep_is_linked(). |
| */ |
| ws = ep_wakeup_source(epi); |
| if (ws) { |
| if (ws->active) |
| __pm_stay_awake(ep->ws); |
| __pm_relax(ws); |
| } |
| |
| list_del_init(&epi->rdllink); |
| |
| /* |
| * If the event mask intersect the caller-requested one, |
| * deliver the event to userspace. Again, we are holding ep->mtx, |
| * so no operations coming from userspace can change the item. |
| */ |
| revents = ep_item_poll(epi, &pt, 1); |
| if (!revents) |
| continue; |
| |
| events = epoll_put_uevent(revents, epi->event.data, events); |
| if (!events) { |
| list_add(&epi->rdllink, &txlist); |
| ep_pm_stay_awake(epi); |
| if (!res) |
| res = -EFAULT; |
| break; |
| } |
| res++; |
| if (epi->event.events & EPOLLONESHOT) |
| epi->event.events &= EP_PRIVATE_BITS; |
| else if (!(epi->event.events & EPOLLET)) { |
| /* |
| * If this file has been added with Level |
| * Trigger mode, we need to insert back inside |
| * the ready list, so that the next call to |
| * epoll_wait() will check again the events |
| * availability. At this point, no one can insert |
| * into ep->rdllist besides us. The epoll_ctl() |
| * callers are locked out by |
| * ep_scan_ready_list() holding "mtx" and the |
| * poll callback will queue them in ep->ovflist. |
| */ |
| list_add_tail(&epi->rdllink, &ep->rdllist); |
| ep_pm_stay_awake(epi); |
| } |
| } |
| ep_done_scan(ep, &txlist); |
| mutex_unlock(&ep->mtx); |
| |
| return res; |
| } |
| |
| static struct timespec64 *ep_timeout_to_timespec(struct timespec64 *to, long ms) |
| { |
| struct timespec64 now; |
| |
| if (ms < 0) |
| return NULL; |
| |
| if (!ms) { |
| to->tv_sec = 0; |
| to->tv_nsec = 0; |
| return to; |
| } |
| |
| to->tv_sec = ms / MSEC_PER_SEC; |
| to->tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC); |
| |
| ktime_get_ts64(&now); |
| *to = timespec64_add_safe(now, *to); |
| return to; |
| } |
| |
| /* |
| * autoremove_wake_function, but remove even on failure to wake up, because we |
| * know that default_wake_function/ttwu will only fail if the thread is already |
| * woken, and in that case the ep_poll loop will remove the entry anyways, not |
| * try to reuse it. |
| */ |
| static int ep_autoremove_wake_function(struct wait_queue_entry *wq_entry, |
| unsigned int mode, int sync, void *key) |
| { |
| int ret = default_wake_function(wq_entry, mode, sync, key); |
| |
| /* |
| * Pairs with list_empty_careful in ep_poll, and ensures future loop |
| * iterations see the cause of this wakeup. |
| */ |
| list_del_init_careful(&wq_entry->entry); |
| return ret; |
| } |
| |
| /** |
| * ep_poll - Retrieves ready events, and delivers them to the caller-supplied |
| * event buffer. |
| * |
| * @ep: Pointer to the eventpoll context. |
| * @events: Pointer to the userspace buffer where the ready events should be |
| * stored. |
| * @maxevents: Size (in terms of number of events) of the caller event buffer. |
| * @timeout: Maximum timeout for the ready events fetch operation, in |
| * timespec. If the timeout is zero, the function will not block, |
| * while if the @timeout ptr is NULL, the function will block |
| * until at least one event has been retrieved (or an error |
| * occurred). |
| * |
| * Return: the number of ready events which have been fetched, or an |
| * error code, in case of error. |
| */ |
| static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events, |
| int maxevents, struct timespec64 *timeout) |
| { |
| int res, eavail, timed_out = 0; |
| u64 slack = 0; |
| wait_queue_entry_t wait; |
| ktime_t expires, *to = NULL; |
| |
| lockdep_assert_irqs_enabled(); |
| |
| if (timeout && (timeout->tv_sec | timeout->tv_nsec)) { |
| slack = select_estimate_accuracy(timeout); |
| to = &expires; |
| *to = timespec64_to_ktime(*timeout); |
| } else if (timeout) { |
| /* |
| * Avoid the unnecessary trip to the wait queue loop, if the |
| * caller specified a non blocking operation. |
| */ |
| timed_out = 1; |
| } |
| |
| /* |
| * This call is racy: We may or may not see events that are being added |
| * to the ready list under the lock (e.g., in IRQ callbacks). For cases |
| * with a non-zero timeout, this thread will check the ready list under |
| * lock and will add to the wait queue. For cases with a zero |
| * timeout, the user by definition should not care and will have to |
| * recheck again. |
| */ |
| eavail = ep_events_available(ep); |
| |
| while (1) { |
| if (eavail) { |
| /* |
| * Try to transfer events to user space. In case we get |
| * 0 events and there's still timeout left over, we go |
| * trying again in search of more luck. |
| */ |
| res = ep_send_events(ep, events, maxevents); |
| if (res) |
| return res; |
| } |
| |
| if (timed_out) |
| return 0; |
| |
| eavail = ep_busy_loop(ep, timed_out); |
| if (eavail) |
| continue; |
| |
| if (signal_pending(current)) |
| return -EINTR; |
| |
| /* |
| * Internally init_wait() uses autoremove_wake_function(), |
| * thus wait entry is removed from the wait queue on each |
| * wakeup. Why it is important? In case of several waiters |
| * each new wakeup will hit the next waiter, giving it the |
| * chance to harvest new event. Otherwise wakeup can be |
| * lost. This is also good performance-wise, because on |
| * normal wakeup path no need to call __remove_wait_queue() |
| * explicitly, thus ep->lock is not taken, which halts the |
| * event delivery. |
| * |
| * In fact, we now use an even more aggressive function that |
| * unconditionally removes, because we don't reuse the wait |
| * entry between loop iterations. This lets us also avoid the |
| * performance issue if a process is killed, causing all of its |
| * threads to wake up without being removed normally. |
| */ |
| init_wait(&wait); |
| wait.func = ep_autoremove_wake_function; |
| |
| write_lock_irq(&ep->lock); |
| /* |
| * Barrierless variant, waitqueue_active() is called under |
| * the same lock on wakeup ep_poll_callback() side, so it |
| * is safe to avoid an explicit barrier. |
| */ |
| __set_current_state(TASK_INTERRUPTIBLE); |
| |
| /* |
| * Do the final check under the lock. ep_scan_ready_list() |
| * plays with two lists (->rdllist and ->ovflist) and there |
| * is always a race when both lists are empty for short |
| * period of time although events are pending, so lock is |
| * important. |
| */ |
| eavail = ep_events_available(ep); |
| if (!eavail) |
| __add_wait_queue_exclusive(&ep->wq, &wait); |
| |
| write_unlock_irq(&ep->lock); |
| |
| if (!eavail) |
| timed_out = !freezable_schedule_hrtimeout_range(to, slack, |
| HRTIMER_MODE_ABS); |
| __set_current_state(TASK_RUNNING); |
| |
| /* |
| * We were woken up, thus go and try to harvest some events. |
| * If timed out and still on the wait queue, recheck eavail |
| * carefully under lock, below. |
| */ |
| eavail = 1; |
| |
| if (!list_empty_careful(&wait.entry)) { |
| write_lock_irq(&ep->lock); |
| /* |
| * If the thread timed out and is not on the wait queue, |
| * it means that the thread was woken up after its |
| * timeout expired before it could reacquire the lock. |
| * Thus, when wait.entry is empty, it needs to harvest |
| * events. |
| */ |
| if (timed_out) |
| eavail = list_empty(&wait.entry); |
| __remove_wait_queue(&ep->wq, &wait); |
| write_unlock_irq(&ep->lock); |
| } |
| } |
| } |
| |
| /** |
| * ep_loop_check_proc - verify that adding an epoll file inside another |
| * epoll structure does not violate the constraints, in |
| * terms of closed loops, or too deep chains (which can |
| * result in excessive stack usage). |
| * |
| * @ep: the &struct eventpoll to be currently checked. |
| * @depth: Current depth of the path being checked. |
| * |
| * Return: %zero if adding the epoll @file inside current epoll |
| * structure @ep does not violate the constraints, or %-1 otherwise. |
| */ |
| static int ep_loop_check_proc(struct eventpoll *ep, int depth) |
| { |
| int error = 0; |
| struct rb_node *rbp; |
| struct epitem *epi; |
| |
| mutex_lock_nested(&ep->mtx, depth + 1); |
| ep->gen = loop_check_gen; |
| for (rbp = rb_first_cached(&ep->rbr); rbp; rbp = rb_next(rbp)) { |
| epi = rb_entry(rbp, struct epitem, rbn); |
| if (unlikely(is_file_epoll(epi->ffd.file))) { |
| struct eventpoll *ep_tovisit; |
| ep_tovisit = epi->ffd.file->private_data; |
| if (ep_tovisit->gen == loop_check_gen) |
| continue; |
| if (ep_tovisit == inserting_into || depth > EP_MAX_NESTS) |
| error = -1; |
| else |
| error = ep_loop_check_proc(ep_tovisit, depth + 1); |
| if (error != 0) |
| break; |
| } else { |
| /* |
| * If we've reached a file that is not associated with |
| * an ep, then we need to check if the newly added |
| * links are going to add too many wakeup paths. We do |
| * this by adding it to the tfile_check_list, if it's |
| * not already there, and calling reverse_path_check() |
| * during ep_insert(). |
| */ |
| list_file(epi->ffd.file); |
| } |
| } |
| mutex_unlock(&ep->mtx); |
| |
| return error; |
| } |
| |
| /** |
| * ep_loop_check - Performs a check to verify that adding an epoll file (@to) |
| * into another epoll file (represented by @ep) does not create |
| * closed loops or too deep chains. |
| * |
| * @ep: Pointer to the epoll we are inserting into. |
| * @to: Pointer to the epoll to be inserted. |
| * |
| * Return: %zero if adding the epoll @to inside the epoll @from |
| * does not violate the constraints, or %-1 otherwise. |
| */ |
| static int ep_loop_check(struct eventpoll *ep, struct eventpoll *to) |
| { |
| inserting_into = ep; |
| return ep_loop_check_proc(to, 0); |
| } |
| |
| static void clear_tfile_check_list(void) |
| { |
| rcu_read_lock(); |
| while (tfile_check_list != EP_UNACTIVE_PTR) { |
| struct epitems_head *head = tfile_check_list; |
| tfile_check_list = head->next; |
| unlist_file(head); |
| } |
| rcu_read_unlock(); |
| } |
| |
| /* |
| * Open an eventpoll file descriptor. |
| */ |
| static int do_epoll_create(int flags) |
| { |
| int error, fd; |
| struct eventpoll *ep = NULL; |
| struct file *file; |
| |
| /* Check the EPOLL_* constant for consistency. */ |
| BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC); |
| |
| if (flags & ~EPOLL_CLOEXEC) |
| return -EINVAL; |
| /* |
| * Create the internal data structure ("struct eventpoll"). |
| */ |
| error = ep_alloc(&ep); |
| if (error < 0) |
| return error; |
| /* |
| * Creates all the items needed to setup an eventpoll file. That is, |
| * a file structure and a free file descriptor. |
| */ |
| fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC)); |
| if (fd < 0) { |
| error = fd; |
| goto out_free_ep; |
| } |
| file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep, |
| O_RDWR | (flags & O_CLOEXEC)); |
| if (IS_ERR(file)) { |
| error = PTR_ERR(file); |
| goto out_free_fd; |
| } |
| ep->file = file; |
| fd_install(fd, file); |
| return fd; |
| |
| out_free_fd: |
| put_unused_fd(fd); |
| out_free_ep: |
| ep_free(ep); |
| return error; |
| } |
| |
| SYSCALL_DEFINE1(epoll_create1, int, flags) |
| { |
| return do_epoll_create(flags); |
| } |
| |
| SYSCALL_DEFINE1(epoll_create, int, size) |
| { |
| if (size <= 0) |
| return -EINVAL; |
| |
| return do_epoll_create(0); |
| } |
| |
| static inline int epoll_mutex_lock(struct mutex *mutex, int depth, |
| bool nonblock) |
| { |
| if (!nonblock) { |
| mutex_lock_nested(mutex, depth); |
| return 0; |
| } |
| if (mutex_trylock(mutex)) |
| return 0; |
| return -EAGAIN; |
| } |
| |
| int do_epoll_ctl(int epfd, int op, int fd, struct epoll_event *epds, |
| bool nonblock) |
| { |
| int error; |
| int full_check = 0; |
| struct fd f, tf; |
| struct eventpoll *ep; |
| struct epitem *epi; |
| struct eventpoll *tep = NULL; |
| |
| error = -EBADF; |
| f = fdget(epfd); |
| if (!f.file) |
| goto error_return; |
| |
| /* Get the "struct file *" for the target file */ |
| tf = fdget(fd); |
| if (!tf.file) |
| goto error_fput; |
| |
| /* The target file descriptor must support poll */ |
| error = -EPERM; |
| if (!file_can_poll(tf.file)) |
| goto error_tgt_fput; |
| |
| /* Check if EPOLLWAKEUP is allowed */ |
| if (ep_op_has_event(op)) |
| ep_take_care_of_epollwakeup(epds); |
| |
| /* |
| * We have to check that the file structure underneath the file descriptor |
| * the user passed to us _is_ an eventpoll file. And also we do not permit |
| * adding an epoll file descriptor inside itself. |
| */ |
| error = -EINVAL; |
| if (f.file == tf.file || !is_file_epoll(f.file)) |
| goto error_tgt_fput; |
| |
| /* |
| * epoll adds to the wakeup queue at EPOLL_CTL_ADD time only, |
| * so EPOLLEXCLUSIVE is not allowed for a EPOLL_CTL_MOD operation. |
| * Also, we do not currently supported nested exclusive wakeups. |
| */ |
| if (ep_op_has_event(op) && (epds->events & EPOLLEXCLUSIVE)) { |
| if (op == EPOLL_CTL_MOD) |
| goto error_tgt_fput; |
| if (op == EPOLL_CTL_ADD && (is_file_epoll(tf.file) || |
| (epds->events & ~EPOLLEXCLUSIVE_OK_BITS))) |
| goto error_tgt_fput; |
| } |
| |
| /* |
| * At this point it is safe to assume that the "private_data" contains |
| * our own data structure. |
| */ |
| ep = f.file->private_data; |
| |
| /* |
| * When we insert an epoll file descriptor inside another epoll file |
| * descriptor, there is the chance of creating closed loops, which are |
| * better be handled here, than in more critical paths. While we are |
| * checking for loops we also determine the list of files reachable |
| * and hang them on the tfile_check_list, so we can check that we |
| * haven't created too many possible wakeup paths. |
| * |
| * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when |
| * the epoll file descriptor is attaching directly to a wakeup source, |
| * unless the epoll file descriptor is nested. The purpose of taking the |
| * 'epmutex' on add is to prevent complex toplogies such as loops and |
| * deep wakeup paths from forming in parallel through multiple |
| * EPOLL_CTL_ADD operations. |
| */ |
| error = epoll_mutex_lock(&ep->mtx, 0, nonblock); |
| if (error) |
| goto error_tgt_fput; |
| if (op == EPOLL_CTL_ADD) { |
| if (READ_ONCE(f.file->f_ep) || ep->gen == loop_check_gen || |
| is_file_epoll(tf.file)) { |
| mutex_unlock(&ep->mtx); |
| error = epoll_mutex_lock(&epmutex, 0, nonblock); |
| if (error) |
| goto error_tgt_fput; |
| loop_check_gen++; |
| full_check = 1; |
| if (is_file_epoll(tf.file)) { |
| tep = tf.file->private_data; |
| error = -ELOOP; |
| if (ep_loop_check(ep, tep) != 0) |
| goto error_tgt_fput; |
| } |
| error = epoll_mutex_lock(&ep->mtx, 0, nonblock); |
| if (error) |
| goto error_tgt_fput; |
| } |
| } |
| |
| /* |
| * Try to lookup the file inside our RB tree. Since we grabbed "mtx" |
| * above, we can be sure to be able to use the item looked up by |
| * ep_find() till we release the mutex. |
| */ |
| epi = ep_find(ep, tf.file, fd); |
| |
| error = -EINVAL; |
| switch (op) { |
| case EPOLL_CTL_ADD: |
| if (!epi) { |
| epds->events |= EPOLLERR | EPOLLHUP; |
| error = ep_insert(ep, epds, tf.file, fd, full_check); |
| } else |
| error = -EEXIST; |
| break; |
| case EPOLL_CTL_DEL: |
| if (epi) |
| error = ep_remove(ep, epi); |
| else |
| error = -ENOENT; |
| break; |
| case EPOLL_CTL_MOD: |
| if (epi) { |
| if (!(epi->event.events & EPOLLEXCLUSIVE)) { |
| epds->events |= EPOLLERR | EPOLLHUP; |
| error = ep_modify(ep, epi, epds); |
| } |
| } else |
| error = -ENOENT; |
| break; |
| } |
| mutex_unlock(&ep->mtx); |
| |
| error_tgt_fput: |
| if (full_check) { |
| clear_tfile_check_list(); |
| loop_check_gen++; |
| mutex_unlock(&epmutex); |
| } |
| |
| fdput(tf); |
| error_fput: |
| fdput(f); |
| error_return: |
| |
| return error; |
| } |
| |
| /* |
| * The following function implements the controller interface for |
| * the eventpoll file that enables the insertion/removal/change of |
| * file descriptors inside the interest set. |
| */ |
| SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, |
| struct epoll_event __user *, event) |
| { |
| struct epoll_event epds; |
| |
| if (ep_op_has_event(op) && |
| copy_from_user(&epds, event, sizeof(struct epoll_event))) |
| return -EFAULT; |
| |
| return do_epoll_ctl(epfd, op, fd, &epds, false); |
| } |
| |
| /* |
| * Implement the event wait interface for the eventpoll file. It is the kernel |
| * part of the user space epoll_wait(2). |
| */ |
| static int do_epoll_wait(int epfd, struct epoll_event __user *events, |
| int maxevents, struct timespec64 *to) |
| { |
| int error; |
| struct fd f; |
| struct eventpoll *ep; |
| |
| /* The maximum number of event must be greater than zero */ |
| if (maxevents <= 0 || maxevents > EP_MAX_EVENTS) |
| return -EINVAL; |
| |
| /* Verify that the area passed by the user is writeable */ |
| if (!access_ok(events, maxevents * sizeof(struct epoll_event))) |
| return -EFAULT; |
| |
| /* Get the "struct file *" for the eventpoll file */ |
| f = fdget(epfd); |
| if (!f.file) |
| return -EBADF; |
| |
| /* |
| * We have to check that the file structure underneath the fd |
| * the user passed to us _is_ an eventpoll file. |
| */ |
| error = -EINVAL; |
| if (!is_file_epoll(f.file)) |
| goto error_fput; |
| |
| /* |
| * At this point it is safe to assume that the "private_data" contains |
| * our own data structure. |
| */ |
| ep = f.file->private_data; |
| |
| /* Time to fish for events ... */ |
| error = ep_poll(ep, events, maxevents, to); |
| |
| error_fput: |
| fdput(f); |
| return error; |
| } |
| |
| SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events, |
| int, maxevents, int, timeout) |
| { |
| struct timespec64 to; |
| |
| return do_epoll_wait(epfd, events, maxevents, |
| ep_timeout_to_timespec(&to, timeout)); |
| } |
| |
| /* |
| * Implement the event wait interface for the eventpoll file. It is the kernel |
| * part of the user space epoll_pwait(2). |
| */ |
| static int do_epoll_pwait(int epfd, struct epoll_event __user *events, |
| int maxevents, struct timespec64 *to, |
| const sigset_t __user *sigmask, size_t sigsetsize) |
| { |
| int error; |
| |
| /* |
| * If the caller wants a certain signal mask to be set during the wait, |
| * we apply it here. |
| */ |
| error = set_user_sigmask(sigmask, sigsetsize); |
| if (error) |
| return error; |
| |
| error = do_epoll_wait(epfd, events, maxevents, to); |
| |
| restore_saved_sigmask_unless(error == -EINTR); |
| |
| return error; |
| } |
| |
| SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events, |
| int, maxevents, int, timeout, const sigset_t __user *, sigmask, |
| size_t, sigsetsize) |
| { |
| struct timespec64 to; |
| |
| return do_epoll_pwait(epfd, events, maxevents, |
| ep_timeout_to_timespec(&to, timeout), |
| sigmask, sigsetsize); |
| } |
| |
| SYSCALL_DEFINE6(epoll_pwait2, int, epfd, struct epoll_event __user *, events, |
| int, maxevents, const struct __kernel_timespec __user *, timeout, |
| const sigset_t __user *, sigmask, size_t, sigsetsize) |
| { |
| struct timespec64 ts, *to = NULL; |
| |
| if (timeout) { |
| if (get_timespec64(&ts, timeout)) |
| return -EFAULT; |
| to = &ts; |
| if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) |
| return -EINVAL; |
| } |
| |
| return do_epoll_pwait(epfd, events, maxevents, to, |
| sigmask, sigsetsize); |
| } |
| |
| #ifdef CONFIG_COMPAT |
| static int do_compat_epoll_pwait(int epfd, struct epoll_event __user *events, |
| int maxevents, struct timespec64 *timeout, |
| const compat_sigset_t __user *sigmask, |
| compat_size_t sigsetsize) |
| { |
| long err; |
| |
| /* |
| * If the caller wants a certain signal mask to be set during the wait, |
| * we apply it here. |
| */ |
| err = set_compat_user_sigmask(sigmask, sigsetsize); |
| if (err) |
| return err; |
| |
| err = do_epoll_wait(epfd, events, maxevents, timeout); |
| |
| restore_saved_sigmask_unless(err == -EINTR); |
| |
| return err; |
| } |
| |
| COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd, |
| struct epoll_event __user *, events, |
| int, maxevents, int, timeout, |
| const compat_sigset_t __user *, sigmask, |
| compat_size_t, sigsetsize) |
| { |
| struct timespec64 to; |
| |
| return do_compat_epoll_pwait(epfd, events, maxevents, |
| ep_timeout_to_timespec(&to, timeout), |
| sigmask, sigsetsize); |
| } |
| |
| COMPAT_SYSCALL_DEFINE6(epoll_pwait2, int, epfd, |
| struct epoll_event __user *, events, |
| int, maxevents, |
| const struct __kernel_timespec __user *, timeout, |
| const compat_sigset_t __user *, sigmask, |
| compat_size_t, sigsetsize) |
| { |
| struct timespec64 ts, *to = NULL; |
| |
| if (timeout) { |
| if (get_timespec64(&ts, timeout)) |
| return -EFAULT; |
| to = &ts; |
| if (poll_select_set_timeout(to, ts.tv_sec, ts.tv_nsec)) |
| return -EINVAL; |
| } |
| |
| return do_compat_epoll_pwait(epfd, events, maxevents, to, |
| sigmask, sigsetsize); |
| } |
| |
| #endif |
| |
| static int __init eventpoll_init(void) |
| { |
| struct sysinfo si; |
| |
| si_meminfo(&si); |
| /* |
| * Allows top 4% of lomem to be allocated for epoll watches (per user). |
| */ |
| max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) / |
| EP_ITEM_COST; |
| BUG_ON(max_user_watches < 0); |
| |
| /* |
| * We can have many thousands of epitems, so prevent this from |
| * using an extra cache line on 64-bit (and smaller) CPUs |
| */ |
| BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128); |
| |
| /* Allocates slab cache used to allocate "struct epitem" items */ |
| epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem), |
| 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); |
| |
| /* Allocates slab cache used to allocate "struct eppoll_entry" */ |
| pwq_cache = kmem_cache_create("eventpoll_pwq", |
| sizeof(struct eppoll_entry), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); |
| |
| ephead_cache = kmem_cache_create("ep_head", |
| sizeof(struct epitems_head), 0, SLAB_PANIC|SLAB_ACCOUNT, NULL); |
| |
| return 0; |
| } |
| fs_initcall(eventpoll_init); |