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authorJamie Liu <jamieliu@google.com>2020-04-08 13:39:02 -0700
committergVisor bot <gvisor-bot@google.com>2020-04-08 13:40:27 -0700
commitd8c0c1d9d5f30f4cfe8e0adedd264b10aff793f7 (patch)
tree0ccbdd57c333bd6b629c9f6e8e9494a6ef8a2c6c /pkg/sentry/fsimpl/proc
parentb30130567d81157e39b692e0116f86015f0bcc71 (diff)
Do not hold FileDescription references in VFS2 procfs inodes.
FileDescription references are side-effectual; for example, holding a reference on the write end of a pipe prevents reads from the read end from returning EOF. This change is consistent with Linux, but not VFS1; while VFS1 also has this bug, it's less visible there since VFS1 procfs disables caching. Updates #1195 PiperOrigin-RevId: 305545099
Diffstat (limited to 'pkg/sentry/fsimpl/proc')
-rw-r--r--pkg/sentry/fsimpl/proc/task_fds.go125
1 files changed, 67 insertions, 58 deletions
diff --git a/pkg/sentry/fsimpl/proc/task_fds.go b/pkg/sentry/fsimpl/proc/task_fds.go
index 9c8656b28..046265eca 100644
--- a/pkg/sentry/fsimpl/proc/task_fds.go
+++ b/pkg/sentry/fsimpl/proc/task_fds.go
@@ -30,34 +30,35 @@ import (
"gvisor.dev/gvisor/pkg/syserror"
)
-type fdDir struct {
- inoGen InoGenerator
- task *kernel.Task
-
- // When produceSymlinks is set, dirents produces for the FDs are reported
- // as symlink. Otherwise, they are reported as regular files.
- produceSymlink bool
-}
-
-func (i *fdDir) lookup(name string) (*vfs.FileDescription, kernel.FDFlags, error) {
- fd, err := strconv.ParseUint(name, 10, 64)
- if err != nil {
- return nil, kernel.FDFlags{}, syserror.ENOENT
- }
-
+func getTaskFD(t *kernel.Task, fd int32) (*vfs.FileDescription, kernel.FDFlags) {
var (
file *vfs.FileDescription
flags kernel.FDFlags
)
- i.task.WithMuLocked(func(t *kernel.Task) {
- if fdTable := t.FDTable(); fdTable != nil {
- file, flags = fdTable.GetVFS2(int32(fd))
+ t.WithMuLocked(func(t *kernel.Task) {
+ if fdt := t.FDTable(); fdt != nil {
+ file, flags = fdt.GetVFS2(fd)
}
})
+ return file, flags
+}
+
+func taskFDExists(t *kernel.Task, fd int32) bool {
+ file, _ := getTaskFD(t, fd)
if file == nil {
- return nil, kernel.FDFlags{}, syserror.ENOENT
+ return false
}
- return file, flags, nil
+ file.DecRef()
+ return true
+}
+
+type fdDir struct {
+ inoGen InoGenerator
+ task *kernel.Task
+
+ // When produceSymlinks is set, dirents produces for the FDs are reported
+ // as symlink. Otherwise, they are reported as regular files.
+ produceSymlink bool
}
// IterDirents implements kernfs.inodeDynamicLookup.
@@ -128,11 +129,15 @@ func newFDDirInode(task *kernel.Task, inoGen InoGenerator) *kernfs.Dentry {
// Lookup implements kernfs.inodeDynamicLookup.
func (i *fdDirInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, error) {
- file, _, err := i.lookup(name)
+ fdInt, err := strconv.ParseInt(name, 10, 32)
if err != nil {
- return nil, err
+ return nil, syserror.ENOENT
+ }
+ fd := int32(fdInt)
+ if !taskFDExists(i.task, fd) {
+ return nil, syserror.ENOENT
}
- taskDentry := newFDSymlink(i.task.Credentials(), file, i.inoGen.NextIno())
+ taskDentry := newFDSymlink(i.task, fd, i.inoGen.NextIno())
return taskDentry.VFSDentry(), nil
}
@@ -169,19 +174,22 @@ func (i *fdDirInode) CheckPermissions(ctx context.Context, creds *auth.Credentia
//
// +stateify savable
type fdSymlink struct {
- refs.AtomicRefCount
kernfs.InodeAttrs
+ kernfs.InodeNoopRefCount
kernfs.InodeSymlink
- file *vfs.FileDescription
+ task *kernel.Task
+ fd int32
}
var _ kernfs.Inode = (*fdSymlink)(nil)
-func newFDSymlink(creds *auth.Credentials, file *vfs.FileDescription, ino uint64) *kernfs.Dentry {
- file.IncRef()
- inode := &fdSymlink{file: file}
- inode.Init(creds, ino, linux.ModeSymlink|0777)
+func newFDSymlink(task *kernel.Task, fd int32, ino uint64) *kernfs.Dentry {
+ inode := &fdSymlink{
+ task: task,
+ fd: fd,
+ }
+ inode.Init(task.Credentials(), ino, linux.ModeSymlink|0777)
d := &kernfs.Dentry{}
d.Init(inode)
@@ -189,29 +197,27 @@ func newFDSymlink(creds *auth.Credentials, file *vfs.FileDescription, ino uint64
}
func (s *fdSymlink) Readlink(ctx context.Context) (string, error) {
+ file, _ := getTaskFD(s.task, s.fd)
+ if file == nil {
+ return "", syserror.ENOENT
+ }
+ defer file.DecRef()
root := vfs.RootFromContext(ctx)
defer root.DecRef()
-
- vfsObj := s.file.VirtualDentry().Mount().Filesystem().VirtualFilesystem()
- return vfsObj.PathnameWithDeleted(ctx, root, s.file.VirtualDentry())
+ return s.task.Kernel().VFS().PathnameWithDeleted(ctx, root, file.VirtualDentry())
}
func (s *fdSymlink) Getlink(ctx context.Context) (vfs.VirtualDentry, string, error) {
- vd := s.file.VirtualDentry()
+ file, _ := getTaskFD(s.task, s.fd)
+ if file == nil {
+ return vfs.VirtualDentry{}, "", syserror.ENOENT
+ }
+ defer file.DecRef()
+ vd := file.VirtualDentry()
vd.IncRef()
return vd, "", nil
}
-func (s *fdSymlink) DecRef() {
- s.AtomicRefCount.DecRefWithDestructor(func() {
- s.Destroy()
- })
-}
-
-func (s *fdSymlink) Destroy() {
- s.file.DecRef()
-}
-
// fdInfoDirInode represents the inode for /proc/[pid]/fdinfo directory.
//
// +stateify savable
@@ -244,12 +250,18 @@ func newFDInfoDirInode(task *kernel.Task, inoGen InoGenerator) *kernfs.Dentry {
// Lookup implements kernfs.inodeDynamicLookup.
func (i *fdInfoDirInode) Lookup(ctx context.Context, name string) (*vfs.Dentry, error) {
- file, flags, err := i.lookup(name)
+ fdInt, err := strconv.ParseInt(name, 10, 32)
if err != nil {
- return nil, err
+ return nil, syserror.ENOENT
+ }
+ fd := int32(fdInt)
+ if !taskFDExists(i.task, fd) {
+ return nil, syserror.ENOENT
+ }
+ data := &fdInfoData{
+ task: i.task,
+ fd: fd,
}
-
- data := &fdInfoData{file: file, flags: flags}
dentry := newTaskOwnedFile(i.task, i.inoGen.NextIno(), 0444, data)
return dentry.VFSDentry(), nil
}
@@ -268,26 +280,23 @@ type fdInfoData struct {
kernfs.DynamicBytesFile
refs.AtomicRefCount
- file *vfs.FileDescription
- flags kernel.FDFlags
+ task *kernel.Task
+ fd int32
}
var _ dynamicInode = (*fdInfoData)(nil)
-func (d *fdInfoData) DecRef() {
- d.AtomicRefCount.DecRefWithDestructor(d.destroy)
-}
-
-func (d *fdInfoData) destroy() {
- d.file.DecRef()
-}
-
// Generate implements vfs.DynamicBytesSource.Generate.
func (d *fdInfoData) Generate(ctx context.Context, buf *bytes.Buffer) error {
+ file, descriptorFlags := getTaskFD(d.task, d.fd)
+ if file == nil {
+ return syserror.ENOENT
+ }
+ defer file.DecRef()
// TODO(b/121266871): Include pos, locks, and other data. For now we only
// have flags.
// See https://www.kernel.org/doc/Documentation/filesystems/proc.txt
- flags := uint(d.file.StatusFlags()) | d.flags.ToLinuxFileFlags()
+ flags := uint(file.StatusFlags()) | descriptorFlags.ToLinuxFileFlags()
fmt.Fprintf(buf, "flags:\t0%o\n", flags)
return nil
}