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-rw-r--r--pkg/sentry/fsimpl/gofer/BUILD3
-rw-r--r--pkg/sentry/fsimpl/gofer/filesystem.go56
-rw-r--r--pkg/sentry/fsimpl/gofer/host_named_pipe.go97
-rw-r--r--pkg/sentry/fsimpl/gofer/special_file.go77
4 files changed, 206 insertions, 27 deletions
diff --git a/pkg/sentry/fsimpl/gofer/BUILD b/pkg/sentry/fsimpl/gofer/BUILD
index 67e916525..f5f35a3bc 100644
--- a/pkg/sentry/fsimpl/gofer/BUILD
+++ b/pkg/sentry/fsimpl/gofer/BUILD
@@ -35,6 +35,7 @@ go_library(
"fstree.go",
"gofer.go",
"handle.go",
+ "host_named_pipe.go",
"p9file.go",
"regular_file.go",
"socket.go",
@@ -47,6 +48,7 @@ go_library(
"//pkg/abi/linux",
"//pkg/context",
"//pkg/fd",
+ "//pkg/fdnotifier",
"//pkg/fspath",
"//pkg/log",
"//pkg/p9",
@@ -71,6 +73,7 @@ go_library(
"//pkg/unet",
"//pkg/usermem",
"//pkg/waiter",
+ "@org_golang_x_sys//unix:go_default_library",
],
)
diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index 7f2181216..0000ca6ba 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -873,19 +873,37 @@ func (d *dentry) openSpecialFileLocked(ctx context.Context, mnt *vfs.Mount, opts
if opts.Flags&linux.O_DIRECT != 0 {
return nil, syserror.EINVAL
}
- h, err := openHandle(ctx, d.file, ats&vfs.MayRead != 0, ats&vfs.MayWrite != 0, opts.Flags&linux.O_TRUNC != 0)
+ // We assume that the server silently inserts O_NONBLOCK in the open flags
+ // for all named pipes (because all existing gofers do this).
+ //
+ // NOTE(b/133875563): This makes named pipe opens racy, because the
+ // mechanisms for translating nonblocking to blocking opens can only detect
+ // the instantaneous presence of a peer holding the other end of the pipe
+ // open, not whether the pipe was *previously* opened by a peer that has
+ // since closed its end.
+ isBlockingOpenOfNamedPipe := d.fileType() == linux.S_IFIFO && opts.Flags&linux.O_NONBLOCK == 0
+retry:
+ h, err := openHandle(ctx, d.file, ats.MayRead(), ats.MayWrite(), opts.Flags&linux.O_TRUNC != 0)
if err != nil {
+ if isBlockingOpenOfNamedPipe && ats == vfs.MayWrite && err == syserror.ENXIO {
+ // An attempt to open a named pipe with O_WRONLY|O_NONBLOCK fails
+ // with ENXIO if opening the same named pipe with O_WRONLY would
+ // block because there are no readers of the pipe.
+ if err := sleepBetweenNamedPipeOpenChecks(ctx); err != nil {
+ return nil, err
+ }
+ goto retry
+ }
return nil, err
}
- seekable := d.fileType() == linux.S_IFREG
- fd := &specialFileFD{
- handle: h,
- seekable: seekable,
+ if isBlockingOpenOfNamedPipe && ats == vfs.MayRead && h.fd >= 0 {
+ if err := blockUntilNonblockingPipeHasWriter(ctx, h.fd); err != nil {
+ h.close(ctx)
+ return nil, err
+ }
}
- if err := fd.vfsfd.Init(fd, opts.Flags, mnt, &d.vfsd, &vfs.FileDescriptionOptions{
- DenyPRead: !seekable,
- DenyPWrite: !seekable,
- }); err != nil {
+ fd, err := newSpecialFileFD(h, mnt, d, opts.Flags)
+ if err != nil {
h.close(ctx)
return nil, err
}
@@ -981,22 +999,16 @@ func (d *dentry) createAndOpenChildLocked(ctx context.Context, rp *vfs.Resolving
}
childVFSFD = &fd.vfsfd
} else {
- seekable := child.fileType() == linux.S_IFREG
- fd := &specialFileFD{
- handle: handle{
- file: openFile,
- fd: -1,
- },
- seekable: seekable,
+ h := handle{
+ file: openFile,
+ fd: -1,
}
if fdobj != nil {
- fd.handle.fd = int32(fdobj.Release())
+ h.fd = int32(fdobj.Release())
}
- if err := fd.vfsfd.Init(fd, opts.Flags, mnt, &child.vfsd, &vfs.FileDescriptionOptions{
- DenyPRead: !seekable,
- DenyPWrite: !seekable,
- }); err != nil {
- fd.handle.close(ctx)
+ fd, err := newSpecialFileFD(h, mnt, child, opts.Flags)
+ if err != nil {
+ h.close(ctx)
return nil, err
}
childVFSFD = &fd.vfsfd
diff --git a/pkg/sentry/fsimpl/gofer/host_named_pipe.go b/pkg/sentry/fsimpl/gofer/host_named_pipe.go
new file mode 100644
index 000000000..7294de7d6
--- /dev/null
+++ b/pkg/sentry/fsimpl/gofer/host_named_pipe.go
@@ -0,0 +1,97 @@
+// Copyright 2019 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 gofer
+
+import (
+ "fmt"
+ "sync"
+ "time"
+
+ "golang.org/x/sys/unix"
+ "gvisor.dev/gvisor/pkg/context"
+ "gvisor.dev/gvisor/pkg/syserror"
+)
+
+// Global pipe used by blockUntilNonblockingPipeHasWriter since we can't create
+// pipes after sentry initialization due to syscall filters.
+var (
+ tempPipeMu sync.Mutex
+ tempPipeReadFD int
+ tempPipeWriteFD int
+ tempPipeBuf [1]byte
+)
+
+func init() {
+ var pipeFDs [2]int
+ if err := unix.Pipe(pipeFDs[:]); err != nil {
+ panic(fmt.Sprintf("failed to create pipe for gofer.blockUntilNonblockingPipeHasWriter: %v", err))
+ }
+ tempPipeReadFD = pipeFDs[0]
+ tempPipeWriteFD = pipeFDs[1]
+}
+
+func blockUntilNonblockingPipeHasWriter(ctx context.Context, fd int32) error {
+ for {
+ ok, err := nonblockingPipeHasWriter(fd)
+ if err != nil {
+ return err
+ }
+ if ok {
+ return nil
+ }
+ if err := sleepBetweenNamedPipeOpenChecks(ctx); err != nil {
+ return err
+ }
+ }
+}
+
+func nonblockingPipeHasWriter(fd int32) (bool, error) {
+ tempPipeMu.Lock()
+ defer tempPipeMu.Unlock()
+ // Copy 1 byte from fd into the temporary pipe.
+ n, err := unix.Tee(int(fd), tempPipeWriteFD, 1, unix.SPLICE_F_NONBLOCK)
+ if err == syserror.EAGAIN {
+ // The pipe represented by fd is empty, but has a writer.
+ return true, nil
+ }
+ if err != nil {
+ return false, err
+ }
+ if n == 0 {
+ // The pipe represented by fd is empty and has no writer.
+ return false, nil
+ }
+ // The pipe represented by fd is non-empty, so it either has, or has
+ // previously had, a writer. Remove the byte copied to the temporary pipe
+ // before returning.
+ if n, err := unix.Read(tempPipeReadFD, tempPipeBuf[:]); err != nil || n != 1 {
+ panic(fmt.Sprintf("failed to drain pipe for gofer.blockUntilNonblockingPipeHasWriter: got (%d, %v), wanted (1, nil)", n, err))
+ }
+ return true, nil
+}
+
+func sleepBetweenNamedPipeOpenChecks(ctx context.Context) error {
+ t := time.NewTimer(100 * time.Millisecond)
+ defer t.Stop()
+ cancel := ctx.SleepStart()
+ select {
+ case <-t.C:
+ ctx.SleepFinish(true)
+ return nil
+ case <-cancel:
+ ctx.SleepFinish(false)
+ return syserror.ErrInterrupted
+ }
+}
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index a464e6a94..ff6126b87 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -19,17 +19,18 @@ import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
+ "gvisor.dev/gvisor/pkg/fdnotifier"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
+ "gvisor.dev/gvisor/pkg/waiter"
)
-// specialFileFD implements vfs.FileDescriptionImpl for files other than
-// regular files, directories, and symlinks: pipes, sockets, etc. It is also
-// used for regular files when filesystemOptions.specialRegularFiles is in
-// effect. specialFileFD differs from regularFileFD by using per-FD handles
-// instead of shared per-dentry handles, and never buffering I/O.
+// specialFileFD implements vfs.FileDescriptionImpl for pipes, sockets, device
+// special files, and (when filesystemOptions.specialRegularFiles is in effect)
+// regular files. specialFileFD differs from regularFileFD by using per-FD
+// handles instead of shared per-dentry handles, and never buffering I/O.
type specialFileFD struct {
fileDescription
@@ -40,13 +41,47 @@ type specialFileFD struct {
// file offset is significant, i.e. a regular file. seekable is immutable.
seekable bool
+ // mayBlock is true if this file description represents a file for which
+ // queue may send I/O readiness events. mayBlock is immutable.
+ mayBlock bool
+ queue waiter.Queue
+
// If seekable is true, off is the file offset. off is protected by mu.
mu sync.Mutex
off int64
}
+func newSpecialFileFD(h handle, mnt *vfs.Mount, d *dentry, flags uint32) (*specialFileFD, error) {
+ ftype := d.fileType()
+ seekable := ftype == linux.S_IFREG
+ mayBlock := ftype == linux.S_IFIFO || ftype == linux.S_IFSOCK
+ fd := &specialFileFD{
+ handle: h,
+ seekable: seekable,
+ mayBlock: mayBlock,
+ }
+ if mayBlock && h.fd >= 0 {
+ if err := fdnotifier.AddFD(h.fd, &fd.queue); err != nil {
+ return nil, err
+ }
+ }
+ if err := fd.vfsfd.Init(fd, flags, mnt, &d.vfsd, &vfs.FileDescriptionOptions{
+ DenyPRead: !seekable,
+ DenyPWrite: !seekable,
+ }); err != nil {
+ if mayBlock && h.fd >= 0 {
+ fdnotifier.RemoveFD(h.fd)
+ }
+ return nil, err
+ }
+ return fd, nil
+}
+
// Release implements vfs.FileDescriptionImpl.Release.
func (fd *specialFileFD) Release() {
+ if fd.mayBlock && fd.handle.fd >= 0 {
+ fdnotifier.RemoveFD(fd.handle.fd)
+ }
fd.handle.close(context.Background())
fs := fd.vfsfd.Mount().Filesystem().Impl().(*filesystem)
fs.syncMu.Lock()
@@ -62,6 +97,32 @@ func (fd *specialFileFD) OnClose(ctx context.Context) error {
return fd.handle.file.flush(ctx)
}
+// Readiness implements waiter.Waitable.Readiness.
+func (fd *specialFileFD) Readiness(mask waiter.EventMask) waiter.EventMask {
+ if fd.mayBlock {
+ return fdnotifier.NonBlockingPoll(fd.handle.fd, mask)
+ }
+ return fd.fileDescription.Readiness(mask)
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (fd *specialFileFD) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+ if fd.mayBlock {
+ fd.queue.EventRegister(e, mask)
+ return
+ }
+ fd.fileDescription.EventRegister(e, mask)
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (fd *specialFileFD) EventUnregister(e *waiter.Entry) {
+ if fd.mayBlock {
+ fd.queue.EventUnregister(e)
+ return
+ }
+ fd.fileDescription.EventUnregister(e)
+}
+
// PRead implements vfs.FileDescriptionImpl.PRead.
func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
if fd.seekable && offset < 0 {
@@ -81,6 +142,9 @@ func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
}
buf := make([]byte, dst.NumBytes())
n, err := fd.handle.readToBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
+ if err == syserror.EAGAIN {
+ err = syserror.ErrWouldBlock
+ }
if n == 0 {
return 0, err
}
@@ -130,6 +194,9 @@ func (fd *specialFileFD) PWrite(ctx context.Context, src usermem.IOSequence, off
return 0, err
}
n, err := fd.handle.writeFromBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
+ if err == syserror.EAGAIN {
+ err = syserror.ErrWouldBlock
+ }
return int64(n), err
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 06:35:05 +0000