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-rw-r--r--pkg/sentry/fsimpl/host/host.go110
1 files changed, 75 insertions, 35 deletions
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go
index a54985ef5..17e3d6e9d 100644
--- a/pkg/sentry/fsimpl/host/host.go
+++ b/pkg/sentry/fsimpl/host/host.go
@@ -54,7 +54,7 @@ func NewMount(vfsObj *vfs.VirtualFilesystem) (*vfs.Mount, error) {
}
// ImportFD sets up and returns a vfs.FileDescription from a donated fd.
-func ImportFD(mnt *vfs.Mount, hostFD int, ownerUID auth.KUID, ownerGID auth.KGID, isTTY bool) (*vfs.FileDescription, error) {
+func ImportFD(mnt *vfs.Mount, hostFD int, isTTY bool) (*vfs.FileDescription, error) {
fs, ok := mnt.Filesystem().Impl().(*kernfs.Filesystem)
if !ok {
return nil, fmt.Errorf("can't import host FDs into filesystems of type %T", mnt.Filesystem().Impl())
@@ -78,8 +78,6 @@ func ImportFD(mnt *vfs.Mount, hostFD int, ownerUID auth.KUID, ownerGID auth.KGID
canMap: canMap(uint32(fileType)),
ino: fs.NextIno(),
mode: fileMode,
- uid: ownerUID,
- gid: ownerGID,
// For simplicity, set offset to 0. Technically, we should
// only set to 0 on files that are not seekable (sockets, pipes, etc.),
// and use the offset from the host fd otherwise.
@@ -135,17 +133,20 @@ type inode struct {
// This field is initialized at creation time and is immutable.
ino uint64
- // TODO(gvisor.dev/issue/1672): protect mode, uid, and gid with mutex.
+ // modeMu protects mode.
+ modeMu sync.Mutex
- // mode is the file mode of this inode. Note that this value may become out
- // of date if the mode is changed on the host, e.g. with chmod.
+ // mode is a cached version of the file mode on the host. Note that it may
+ // become out of date if the mode is changed on the host, e.g. with chmod.
+ //
+ // Generally, it is better to retrieve the mode from the host through an
+ // fstat syscall. We only use this value in inode.Mode(), which cannot
+ // return an error, if the syscall to host fails.
+ //
+ // FIXME(b/152294168): Plumb error into Inode.Mode() return value so we
+ // can get rid of this.
mode linux.FileMode
- // uid and gid of the file owner. Note that these refer to the owner of the
- // file created on import, not the fd on the host.
- uid auth.KUID
- gid auth.KGID
-
// offsetMu protects offset.
offsetMu sync.Mutex
@@ -168,12 +169,35 @@ func fileFlagsFromHostFD(fd int) (int, error) {
// CheckPermissions implements kernfs.Inode.
func (i *inode) CheckPermissions(ctx context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
- return vfs.GenericCheckPermissions(creds, ats, i.mode, i.uid, i.gid)
+ mode, uid, gid, err := i.getPermissions()
+ if err != nil {
+ return err
+ }
+ return vfs.GenericCheckPermissions(creds, ats, mode, uid, gid)
}
// Mode implements kernfs.Inode.
func (i *inode) Mode() linux.FileMode {
- return i.mode
+ mode, _, _, err := i.getPermissions()
+ if err != nil {
+ return i.mode
+ }
+
+ return linux.FileMode(mode)
+}
+
+func (i *inode) getPermissions() (linux.FileMode, auth.KUID, auth.KGID, error) {
+ // Retrieve metadata.
+ var s syscall.Stat_t
+ if err := syscall.Fstat(i.hostFD, &s); err != nil {
+ return 0, 0, 0, err
+ }
+
+ // Update cached mode.
+ i.modeMu.Lock()
+ i.mode = linux.FileMode(s.Mode)
+ i.modeMu.Unlock()
+ return linux.FileMode(s.Mode), auth.KUID(s.Uid), auth.KGID(s.Gid), nil
}
// Stat implements kernfs.Inode.
@@ -213,45 +237,51 @@ func (i *inode) Stat(_ *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, erro
ls.Attributes = s.Attributes
ls.AttributesMask = s.Attributes_mask
- if mask|linux.STATX_TYPE != 0 {
+ if mask&linux.STATX_TYPE != 0 {
ls.Mode |= s.Mode & linux.S_IFMT
}
- if mask|linux.STATX_MODE != 0 {
+ if mask&linux.STATX_MODE != 0 {
ls.Mode |= s.Mode &^ linux.S_IFMT
}
- if mask|linux.STATX_NLINK != 0 {
+ if mask&linux.STATX_NLINK != 0 {
ls.Nlink = s.Nlink
}
- if mask|linux.STATX_ATIME != 0 {
+ if mask&linux.STATX_UID != 0 {
+ ls.UID = s.Uid
+ }
+ if mask&linux.STATX_GID != 0 {
+ ls.GID = s.Gid
+ }
+ if mask&linux.STATX_ATIME != 0 {
ls.Atime = unixToLinuxStatxTimestamp(s.Atime)
}
- if mask|linux.STATX_BTIME != 0 {
+ if mask&linux.STATX_BTIME != 0 {
ls.Btime = unixToLinuxStatxTimestamp(s.Btime)
}
- if mask|linux.STATX_CTIME != 0 {
+ if mask&linux.STATX_CTIME != 0 {
ls.Ctime = unixToLinuxStatxTimestamp(s.Ctime)
}
- if mask|linux.STATX_MTIME != 0 {
+ if mask&linux.STATX_MTIME != 0 {
ls.Mtime = unixToLinuxStatxTimestamp(s.Mtime)
}
- if mask|linux.STATX_SIZE != 0 {
+ if mask&linux.STATX_SIZE != 0 {
ls.Size = s.Size
}
- if mask|linux.STATX_BLOCKS != 0 {
+ if mask&linux.STATX_BLOCKS != 0 {
ls.Blocks = s.Blocks
}
- // Use our own internal inode number and file owner.
- if mask|linux.STATX_INO != 0 {
+ // Use our own internal inode number.
+ if mask&linux.STATX_INO != 0 {
ls.Ino = i.ino
}
- if mask|linux.STATX_UID != 0 {
- ls.UID = uint32(i.uid)
- }
- if mask|linux.STATX_GID != 0 {
- ls.GID = uint32(i.gid)
- }
+ // Update cached mode.
+ if (mask&linux.STATX_TYPE != 0) && (mask&linux.STATX_MODE != 0) {
+ i.modeMu.Lock()
+ i.mode = linux.FileMode(s.Mode)
+ i.modeMu.Unlock()
+ }
return ls, nil
}
@@ -274,6 +304,8 @@ func (i *inode) fstat(opts vfs.StatOptions) (linux.Statx, error) {
Mask: linux.STATX_BASIC_STATS,
Blksize: uint32(s.Blksize),
Nlink: uint32(s.Nlink),
+ UID: s.Uid,
+ GID: s.Gid,
Mode: uint16(s.Mode),
Size: uint64(s.Size),
Blocks: uint64(s.Blocks),
@@ -282,15 +314,13 @@ func (i *inode) fstat(opts vfs.StatOptions) (linux.Statx, error) {
Mtime: timespecToStatxTimestamp(s.Mtim),
}
- // Use our own internal inode number and file owner.
+ // Use our own internal inode number.
//
// TODO(gvisor.dev/issue/1672): Use a kernfs-specific device number as well.
// If we use the device number from the host, it may collide with another
// sentry-internal device number. We handle device/inode numbers without
// relying on the host to prevent collisions.
ls.Ino = i.ino
- ls.UID = uint32(i.uid)
- ls.GID = uint32(i.gid)
return ls, nil
}
@@ -306,7 +336,11 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre
if m&^(linux.STATX_MODE|linux.STATX_SIZE|linux.STATX_ATIME|linux.STATX_MTIME) != 0 {
return syserror.EPERM
}
- if err := vfs.CheckSetStat(ctx, creds, &s, i.Mode(), i.uid, i.gid); err != nil {
+ mode, uid, gid, err := i.getPermissions()
+ if err != nil {
+ return err
+ }
+ if err := vfs.CheckSetStat(ctx, creds, &s, mode.Permissions(), uid, gid); err != nil {
return err
}
@@ -314,7 +348,9 @@ func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Cre
if err := syscall.Fchmod(i.hostFD, uint32(s.Mode)); err != nil {
return err
}
+ i.modeMu.Lock()
i.mode = linux.FileMode(s.Mode)
+ i.modeMu.Unlock()
}
if m&linux.STATX_SIZE != 0 {
if err := syscall.Ftruncate(i.hostFD, int64(s.Size)); err != nil {
@@ -351,7 +387,11 @@ func (i *inode) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptio
}
func (i *inode) open(d *vfs.Dentry, mnt *vfs.Mount) (*vfs.FileDescription, error) {
- fileType := i.mode.FileType()
+ mode, _, _, err := i.getPermissions()
+ if err != nil {
+ return nil, err
+ }
+ fileType := mode.FileType()
if fileType == syscall.S_IFSOCK {
if i.isTTY {
return nil, errors.New("cannot use host socket as TTY")
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-05 12:23:40 +0000