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handlers.go
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handlers.go
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// Copyright 2021 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package lisafs
import (
"fmt"
"math"
"strings"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/cleanup"
"gvisor.dev/gvisor/pkg/flipcall"
"gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/marshal/primitive"
"gvisor.dev/gvisor/pkg/p9"
)
const (
allowedOpenFlags = unix.O_ACCMODE | unix.O_TRUNC
setStatSupportedMask = unix.STATX_MODE | unix.STATX_UID | unix.STATX_GID | unix.STATX_SIZE | unix.STATX_ATIME | unix.STATX_MTIME
// unixDirentMaxSize is the maximum size of unix.Dirent for amd64.
unixDirentMaxSize = 280
)
// RPCHandler defines a handler that is invoked when the associated message is
// received. The handler is responsible for:
//
// - Unmarshalling the request from the passed payload and interpreting it.
// - Marshalling the response into the communicator's payload buffer.
// - Return the number of payload bytes written.
// - Donate any FDs (if needed) to comm which will in turn donate it to client.
type RPCHandler func(c *Connection, comm Communicator, payloadLen uint32) (uint32, error)
var handlers = [...]RPCHandler{
Error: ErrorHandler,
Mount: MountHandler,
Channel: ChannelHandler,
FStat: FStatHandler,
SetStat: SetStatHandler,
Walk: WalkHandler,
WalkStat: WalkStatHandler,
OpenAt: OpenAtHandler,
OpenCreateAt: OpenCreateAtHandler,
Close: CloseHandler,
FSync: FSyncHandler,
PWrite: PWriteHandler,
PRead: PReadHandler,
MkdirAt: MkdirAtHandler,
MknodAt: MknodAtHandler,
SymlinkAt: SymlinkAtHandler,
LinkAt: LinkAtHandler,
FStatFS: FStatFSHandler,
FAllocate: FAllocateHandler,
ReadLinkAt: ReadLinkAtHandler,
Flush: FlushHandler,
UnlinkAt: UnlinkAtHandler,
RenameAt: RenameAtHandler,
Getdents64: Getdents64Handler,
FGetXattr: FGetXattrHandler,
FSetXattr: FSetXattrHandler,
FListXattr: FListXattrHandler,
FRemoveXattr: FRemoveXattrHandler,
Connect: ConnectHandler,
BindAt: BindAtHandler,
Listen: ListenHandler,
Accept: AcceptHandler,
}
// ErrorHandler handles Error message.
func ErrorHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
// Client should never send Error.
return 0, unix.EINVAL
}
// MountHandler handles the Mount RPC. Note that there can not be concurrent
// executions of MountHandler on a connection because the connection enforces
// that Mount is the first message on the connection. Only after the connection
// has been successfully mounted can other channels be created.
func MountHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var (
mountPointFD *ControlFD
mountPointHostFD = -1
mountPointStat linux.Statx
mountNode = c.server.root
)
if err := c.server.withRenameReadLock(func() (err error) {
// Maintain extra ref on mountNode to ensure existence during walk.
mountNode.IncRef()
defer func() {
// Drop extra ref on mountNode. Wrap the defer call with a func so that
// mountNode is evaluated on execution, not on defer itself.
mountNode.DecRef(nil)
}()
// Walk to the mountpoint.
pit := fspath.Parse(c.mountPath).Begin
for pit.Ok() {
curName := pit.String()
if err := checkSafeName(curName); err != nil {
return err
}
mountNode.opMu.RLock()
if mountNode.isDeleted() {
mountNode.opMu.RUnlock()
return unix.ENOENT
}
mountNode.childrenMu.Lock()
next := mountNode.LookupChildLocked(curName)
if next == nil {
next = &Node{}
next.InitLocked(curName, mountNode)
} else {
next.IncRef()
}
mountNode.childrenMu.Unlock()
mountNode.opMu.RUnlock()
// next has an extra ref as needed. Drop extra ref on mountNode.
mountNode.DecRef(nil)
pit = pit.Next()
mountNode = next
}
// Provide Mount with read concurrency guarantee.
mountNode.opMu.RLock()
defer mountNode.opMu.RUnlock()
if mountNode.isDeleted() {
return unix.ENOENT
}
mountPointFD, mountPointStat, mountPointHostFD, err = c.ServerImpl().Mount(c, mountNode)
return err
}); err != nil {
return 0, err
}
if mountPointHostFD >= 0 {
comm.DonateFD(mountPointHostFD)
}
resp := MountResp{
Root: Inode{
ControlFD: mountPointFD.id,
Stat: mountPointStat,
},
SupportedMs: c.ServerImpl().SupportedMessages(),
MaxMessageSize: primitive.Uint32(c.ServerImpl().MaxMessageSize()),
}
respPayloadLen := uint32(resp.SizeBytes())
resp.MarshalBytes(comm.PayloadBuf(respPayloadLen))
return respPayloadLen, nil
}
// ChannelHandler handles the Channel RPC.
func ChannelHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
ch, desc, fdSock, err := c.createChannel(c.ServerImpl().MaxMessageSize())
if err != nil {
return 0, err
}
// Start servicing the channel in a separate goroutine.
c.activeWg.Add(1)
go func() {
if err := c.service(ch); err != nil {
// Don't log shutdown error which is expected during server shutdown.
if _, ok := err.(flipcall.ShutdownError); !ok {
log.Warningf("lisafs.Connection.service(channel = @%p): %v", ch, err)
}
}
c.activeWg.Done()
}()
clientDataFD, err := unix.Dup(desc.FD)
if err != nil {
unix.Close(fdSock)
ch.shutdown()
return 0, err
}
// Respond to client with successful channel creation message.
comm.DonateFD(clientDataFD)
comm.DonateFD(fdSock)
resp := ChannelResp{
dataOffset: desc.Offset,
dataLength: uint64(desc.Length),
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// FStatHandler handles the FStat RPC.
func FStatHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req StatReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
var resp linux.Statx
switch t := fd.(type) {
case *ControlFD:
t.safelyRead(func() error {
resp, err = t.impl.Stat()
return err
})
case *OpenFD:
t.controlFD.safelyRead(func() error {
resp, err = t.impl.Stat()
return err
})
default:
panic(fmt.Sprintf("unknown fd type %T", t))
}
if err != nil {
return 0, err
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// SetStatHandler handles the SetStat RPC.
func SetStatHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req SetStatReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupControlFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if req.Mask&^setStatSupportedMask != 0 {
return 0, unix.EPERM
}
var resp SetStatResp
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() && !c.server.opts.SetAttrOnDeleted {
return unix.EINVAL
}
failureMask, failureErr := fd.impl.SetStat(req)
resp.FailureMask = failureMask
if failureErr != nil {
resp.FailureErrNo = uint32(p9.ExtractErrno(failureErr))
}
return nil
}); err != nil {
return 0, err
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// WalkHandler handles the Walk RPC.
func WalkHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req WalkReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
startDir, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer startDir.DecRef(nil)
if !startDir.IsDir() {
return 0, unix.ENOTDIR
}
// Manually marshal the inodes into the payload buffer during walk to avoid
// the slice allocation. The memory format should be WalkResp's.
var (
numInodes primitive.Uint16
status = WalkSuccess
)
respMetaSize := status.SizeBytes() + numInodes.SizeBytes()
maxPayloadSize := respMetaSize + (len(req.Path) * (*Inode)(nil).SizeBytes())
if maxPayloadSize > math.MaxUint32 {
// Too much to walk, can't do.
return 0, unix.EIO
}
payloadBuf := comm.PayloadBuf(uint32(maxPayloadSize))
payloadPos := respMetaSize
if err := c.server.withRenameReadLock(func() error {
curDir := startDir
cu := cleanup.Make(func() {
// Destroy all newly created FDs until now. Read the new FDIDs from the
// payload buffer.
buf := comm.PayloadBuf(uint32(maxPayloadSize))[respMetaSize:]
var curIno Inode
for i := 0; i < int(numInodes); i++ {
buf = curIno.UnmarshalBytes(buf)
c.removeControlFDLocked(curIno.ControlFD)
}
})
defer cu.Clean()
for _, name := range req.Path {
if err := checkSafeName(name); err != nil {
return err
}
// Symlinks terminate walk. This client gets the symlink inode, but will
// have to invoke Walk again with the resolved path.
if curDir.IsSymlink() {
status = WalkComponentSymlink
break
}
curDir.node.opMu.RLock()
if curDir.node.isDeleted() {
// It is not safe to walk on a deleted directory. It could have been
// replaced with a malicious symlink.
curDir.node.opMu.RUnlock()
status = WalkComponentDoesNotExist
break
}
child, childStat, err := curDir.impl.Walk(name)
curDir.node.opMu.RUnlock()
if err == unix.ENOENT {
status = WalkComponentDoesNotExist
break
}
if err != nil {
return err
}
// Write inode into payload buffer.
i := Inode{ControlFD: child.id, Stat: childStat}
i.MarshalUnsafe(payloadBuf[payloadPos:])
payloadPos += i.SizeBytes()
numInodes++
curDir = child
}
cu.Release()
return nil
}); err != nil {
return 0, err
}
// WalkResp writes the walk status followed by the number of inodes in the
// beginning.
payloadBuf = status.MarshalUnsafe(payloadBuf)
numInodes.MarshalUnsafe(payloadBuf)
return uint32(payloadPos), nil
}
// WalkStatHandler handles the WalkStat RPC.
func WalkStatHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req WalkReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
startDir, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer startDir.DecRef(nil)
// Note that this fd is allowed to not actually be a directory when the
// only path component to walk is "" (self).
if !startDir.IsDir() {
if len(req.Path) > 1 || (len(req.Path) == 1 && len(req.Path[0]) > 0) {
return 0, unix.ENOTDIR
}
}
for i, name := range req.Path {
// First component is allowed to be "".
if i == 0 && len(name) == 0 {
continue
}
if err := checkSafeName(name); err != nil {
return 0, err
}
}
// We will manually marshal the statx results into the payload buffer as they
// are generated to avoid the slice allocation. The memory format should be
// the same as WalkStatResp's.
var numStats primitive.Uint16
maxPayloadSize := numStats.SizeBytes() + (len(req.Path) * linux.SizeOfStatx)
if maxPayloadSize > math.MaxUint32 {
// Too much to walk, can't do.
return 0, unix.EIO
}
payloadBuf := comm.PayloadBuf(uint32(maxPayloadSize))
payloadPos := numStats.SizeBytes()
if c.server.opts.WalkStatSupported {
if err = startDir.safelyRead(func() error {
return startDir.impl.WalkStat(req.Path, func(s linux.Statx) {
s.MarshalUnsafe(payloadBuf[payloadPos:])
payloadPos += s.SizeBytes()
numStats++
})
}); err != nil {
return 0, err
}
// WalkStatResp writes the number of stats in the beginning.
numStats.MarshalUnsafe(payloadBuf)
return uint32(payloadPos), nil
}
if err = c.server.withRenameReadLock(func() error {
if len(req.Path) > 0 && len(req.Path[0]) == 0 {
startDir.node.opMu.RLock()
stat, err := startDir.impl.Stat()
startDir.node.opMu.RUnlock()
if err != nil {
return err
}
stat.MarshalUnsafe(payloadBuf[payloadPos:])
payloadPos += stat.SizeBytes()
numStats++
req.Path = req.Path[1:]
}
parent := startDir
closeParent := func() {
if parent != startDir {
c.removeControlFDLocked(parent.id)
}
}
defer closeParent()
for _, name := range req.Path {
parent.node.opMu.RLock()
if parent.node.isDeleted() {
// It is not safe to walk on a deleted directory. It could have been
// replaced with a malicious symlink.
parent.node.opMu.RUnlock()
break
}
child, childStat, err := parent.impl.Walk(name)
parent.node.opMu.RUnlock()
if err != nil {
if err == unix.ENOENT {
break
}
return err
}
// Update with next generation.
closeParent()
parent = child
// Write results.
childStat.MarshalUnsafe(payloadBuf[payloadPos:])
payloadPos += childStat.SizeBytes()
numStats++
// Symlinks terminate walk. This client gets the symlink stat result, but
// will have to invoke Walk again with the resolved path.
if childStat.Mode&unix.S_IFMT == unix.S_IFLNK {
break
}
}
return nil
}); err != nil {
return 0, err
}
// WalkStatResp writes the number of stats in the beginning.
numStats.MarshalUnsafe(payloadBuf)
return uint32(payloadPos), nil
}
// OpenAtHandler handles the OpenAt RPC.
func OpenAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req OpenAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
// Only keep allowed open flags.
if allowedFlags := req.Flags & allowedOpenFlags; allowedFlags != req.Flags {
log.Debugf("discarding open flags that are not allowed: old open flags = %d, new open flags = %d", req.Flags, allowedFlags)
req.Flags = allowedFlags
}
accessMode := req.Flags & unix.O_ACCMODE
trunc := req.Flags&unix.O_TRUNC != 0
if c.readonly && (accessMode != unix.O_RDONLY || trunc) {
return 0, unix.EROFS
}
fd, err := c.lookupControlFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if fd.IsDir() {
// Directory is not truncatable and must be opened with O_RDONLY.
if accessMode != unix.O_RDONLY || trunc {
return 0, unix.EISDIR
}
}
var (
openFD *OpenFD
hostOpenFD int
)
if err := fd.safelyRead(func() error {
if fd.node.isDeleted() || fd.IsSymlink() {
return unix.EINVAL
}
openFD, hostOpenFD, err = fd.impl.Open(req.Flags)
return err
}); err != nil {
return 0, err
}
if hostOpenFD >= 0 {
comm.DonateFD(hostOpenFD)
}
resp := OpenAtResp{OpenFD: openFD.id}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// OpenCreateAtHandler handles the OpenCreateAt RPC.
func OpenCreateAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req OpenCreateAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
// Only keep allowed open flags.
if allowedFlags := req.Flags & allowedOpenFlags; allowedFlags != req.Flags {
log.Debugf("discarding open flags that are not allowed: old open flags = %d, new open flags = %d", req.Flags, allowedFlags)
req.Flags = allowedFlags
}
name := string(req.Name)
if err := checkSafeName(name); err != nil {
return 0, err
}
fd, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsDir() {
return 0, unix.ENOTDIR
}
var (
childFD *ControlFD
childStat linux.Statx
openFD *OpenFD
hostOpenFD int
)
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() {
return unix.EINVAL
}
childFD, childStat, openFD, hostOpenFD, err = fd.impl.OpenCreate(req.Mode, req.UID, req.GID, name, uint32(req.Flags))
return err
}); err != nil {
return 0, err
}
if hostOpenFD >= 0 {
comm.DonateFD(hostOpenFD)
}
resp := OpenCreateAtResp{
NewFD: openFD.id,
Child: Inode{
ControlFD: childFD.id,
Stat: childStat,
},
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// CloseHandler handles the Close RPC.
func CloseHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req CloseReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
for _, fd := range req.FDs {
c.removeFD(fd)
}
// There is no response message for this.
return 0, nil
}
// FSyncHandler handles the FSync RPC.
func FSyncHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req FsyncReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
// Return the first error we encounter, but sync everything we can
// regardless.
var retErr error
for _, fdid := range req.FDs {
if err := c.fsyncFD(fdid); err != nil && retErr == nil {
retErr = err
}
}
// There is no response message for this.
return 0, retErr
}
func (c *Connection) fsyncFD(id FDID) error {
fd, err := c.lookupOpenFD(id)
if err != nil {
return err
}
defer fd.DecRef(nil)
return fd.controlFD.safelyRead(func() error {
return fd.impl.Sync()
})
}
// PWriteHandler handles the PWrite RPC.
func PWriteHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req PWriteReq
// Note that it is an optimized Unmarshal operation which avoids any buffer
// allocation and copying. req.Buf just points to payload. This is safe to do
// as the handler owns payload and req's lifetime is limited to the handler.
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupOpenFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.writable {
return 0, unix.EBADF
}
var count uint64
if err := fd.controlFD.safelyWrite(func() error {
count, err = fd.impl.Write(req.Buf, uint64(req.Offset))
return err
}); err != nil {
return 0, err
}
resp := PWriteResp{Count: count}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// PReadHandler handles the PRead RPC.
func PReadHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req PReadReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupOpenFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.readable {
return 0, unix.EBADF
}
// To save an allocation and a copy, we directly read into the payload
// buffer. The rest of the response message is manually marshalled.
var resp PReadResp
respMetaSize := uint32(resp.NumBytes.SizeBytes())
respPayloadLen := respMetaSize + req.Count
if respPayloadLen > c.maxMessageSize {
return 0, unix.ENOBUFS
}
payloadBuf := comm.PayloadBuf(respPayloadLen)
var n uint64
if err := fd.controlFD.safelyRead(func() error {
n, err = fd.impl.Read(payloadBuf[respMetaSize:], req.Offset)
return err
}); err != nil {
return 0, err
}
// Write the response metadata onto the payload buffer. The response contents
// already have been written immediately after it.
resp.NumBytes = primitive.Uint64(n)
resp.NumBytes.MarshalUnsafe(payloadBuf)
return respMetaSize + uint32(n), nil
}
// MkdirAtHandler handles the MkdirAt RPC.
func MkdirAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req MkdirAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
name := string(req.Name)
if err := checkSafeName(name); err != nil {
return 0, err
}
fd, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsDir() {
return 0, unix.ENOTDIR
}
var (
childDir *ControlFD
childDirStat linux.Statx
)
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() {
return unix.EINVAL
}
childDir, childDirStat, err = fd.impl.Mkdir(req.Mode, req.UID, req.GID, name)
return err
}); err != nil {
return 0, err
}
resp := MkdirAtResp{
ChildDir: Inode{
ControlFD: childDir.id,
Stat: childDirStat,
},
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// MknodAtHandler handles the MknodAt RPC.
func MknodAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req MknodAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
name := string(req.Name)
if err := checkSafeName(name); err != nil {
return 0, err
}
fd, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsDir() {
return 0, unix.ENOTDIR
}
var (
child *ControlFD
childStat linux.Statx
)
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() {
return unix.EINVAL
}
child, childStat, err = fd.impl.Mknod(req.Mode, req.UID, req.GID, name, uint32(req.Minor), uint32(req.Major))
return err
}); err != nil {
return 0, err
}
resp := MknodAtResp{
Child: Inode{
ControlFD: child.id,
Stat: childStat,
},
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// SymlinkAtHandler handles the SymlinkAt RPC.
func SymlinkAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req SymlinkAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
name := string(req.Name)
if err := checkSafeName(name); err != nil {
return 0, err
}
fd, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsDir() {
return 0, unix.ENOTDIR
}
var (
symlink *ControlFD
symlinkStat linux.Statx
)
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() {
return unix.EINVAL
}
symlink, symlinkStat, err = fd.impl.Symlink(name, string(req.Target), req.UID, req.GID)
return err
}); err != nil {
return 0, err
}
resp := SymlinkAtResp{
Symlink: Inode{
ControlFD: symlink.id,
Stat: symlinkStat,
},
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// LinkAtHandler handles the LinkAt RPC.
func LinkAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req LinkAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
name := string(req.Name)
if err := checkSafeName(name); err != nil {
return 0, err
}
fd, err := c.lookupControlFD(req.DirFD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsDir() {
return 0, unix.ENOTDIR
}
targetFD, err := c.lookupControlFD(req.Target)
if err != nil {
return 0, err
}
defer targetFD.DecRef(nil)
if targetFD.IsDir() {
// Can not create hard link to directory.
return 0, unix.EPERM
}
var (
link *ControlFD
linkStat linux.Statx
)
if err := fd.safelyWrite(func() error {
if fd.node.isDeleted() {
return unix.EINVAL
}
// This is a lock ordering issue. Need to provide safe read guarantee for
// targetFD. We know targetFD is not a directory while fd is a directory.
// So targetFD would either be a descendant of fd or exist elsewhere in the
// tree. So locking fd first and targetFD later should not lead to cycles.
targetFD.node.opMu.RLock()
defer targetFD.node.opMu.RUnlock()
if targetFD.node.isDeleted() {
return unix.EINVAL
}
link, linkStat, err = targetFD.impl.Link(fd.impl, name)
return err
}); err != nil {
return 0, err
}
resp := LinkAtResp{
Link: Inode{
ControlFD: link.id,
Stat: linkStat,
},
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// FStatFSHandler handles the FStatFS RPC.
func FStatFSHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req FStatFSReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupControlFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
var resp StatFS
if err := fd.safelyRead(func() error {
resp, err = fd.impl.StatFS()
return err
}); err != nil {
return 0, err
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
// FAllocateHandler handles the FAllocate RPC.
func FAllocateHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
if c.readonly {
return 0, unix.EROFS
}
var req FAllocateReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupOpenFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.writable {
return 0, unix.EBADF
}
return 0, fd.controlFD.safelyWrite(func() error {
if fd.controlFD.node.isDeleted() && !c.server.opts.AllocateOnDeleted {
return unix.EINVAL
}
return fd.impl.Allocate(req.Mode, req.Offset, req.Length)
})
}
// ReadLinkAtHandler handles the ReadLinkAt RPC.
func ReadLinkAtHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req ReadLinkAtReq
if _, ok := req.CheckedUnmarshal(comm.PayloadBuf(payloadLen)); !ok {
return 0, unix.EIO
}
fd, err := c.lookupControlFD(req.FD)
if err != nil {
return 0, err
}
defer fd.DecRef(nil)
if !fd.IsSymlink() {
return 0, unix.EINVAL
}
// We will manually marshal ReadLinkAtResp, which just contains a