Add permission checks to vfs2 truncate.

- Check write permission on truncate(2). Unlike ftruncate(2),
  truncate(2) fails if the user does not have write permissions
  on the file.
- For gofers under InteropModeShared, check file type before
  making a truncate request. We should fail early and avoid
  making an rpc when possible. Furthermore, depending on the
  remote host's failure may give us unexpected behavior--if the
  host converts the truncate request to an ftruncate syscall on
  an open fd, we will get EINVAL instead of EISDIR.

Updates #2923.

PiperOrigin-RevId: 322913569

2 files changed, 2 insertions, 2 deletions

diff --git a/pkg/sentry/fsimpl/overlay/filesystem.go b/pkg/sentry/fsimpl/overlay/filesystem.go
index ff82e1f20..6b705e955 100644
--- a/pkg/sentry/fsimpl/overlay/filesystem.go
+++ b/pkg/sentry/fsimpl/overlay/filesystem.go
@@ -1104,7 +1104,7 @@ func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts
 	}
 
 	mode := linux.FileMode(atomic.LoadUint32(&d.mode))
-	if err := vfs.CheckSetStat(ctx, rp.Credentials(), &opts.Stat, mode, auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))); err != nil {
+	if err := vfs.CheckSetStat(ctx, rp.Credentials(), &opts, mode, auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))); err != nil {
 		return err
 	}
 	mnt := rp.Mount()
diff --git a/pkg/sentry/fsimpl/overlay/non_directory.go b/pkg/sentry/fsimpl/overlay/non_directory.go
index 6c8445ea1..c0749e711 100644
--- a/pkg/sentry/fsimpl/overlay/non_directory.go
+++ b/pkg/sentry/fsimpl/overlay/non_directory.go
@@ -151,7 +151,7 @@ func (fd *nonDirectoryFD) Stat(ctx context.Context, opts vfs.StatOptions) (linux
 func (fd *nonDirectoryFD) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
 	d := fd.dentry()
 	mode := linux.FileMode(atomic.LoadUint32(&d.mode))
-	if err := vfs.CheckSetStat(ctx, auth.CredentialsFromContext(ctx), &opts.Stat, mode, auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))); err != nil {
+	if err := vfs.CheckSetStat(ctx, auth.CredentialsFromContext(ctx), &opts, mode, auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))); err != nil {
 		return err
 	}
 	mnt := fd.vfsfd.Mount()