gvisor: return ENOTDIR from the unlink syscall

ENOTDIR has to be returned when a component used as a directory in
pathname is not, in  fact,  a directory.

PiperOrigin-RevId: 269037893

pkg/sentry/fs/dirent.go

@@ -1126,7 +1126,7 @@ func (d *Dirent) unmount(ctx context.Context, replacement *Dirent) error {
 
 // Remove removes the given file or symlink.  The root dirent is used to
 // resolve name, and must not be nil.
-func (d *Dirent) Remove(ctx context.Context, root *Dirent, name string) error {
+func (d *Dirent) Remove(ctx context.Context, root *Dirent, name string, dirPath bool) error {
 	// Check the root.
 	if root == nil {
 		panic("Dirent.Remove: root must not be nil")
@@ -1151,6 +1151,8 @@ func (d *Dirent) Remove(ctx context.Context, root *Dirent, name string) error {
 	// Remove cannot remove directories.
 	if IsDir(child.Inode.StableAttr) {
 		return syscall.EISDIR
+	} else if dirPath {
+		return syscall.ENOTDIR
 	}
 
 	// Remove cannot remove a mount point.

pkg/sentry/fs/dirent_refs_test.go

@@ -343,7 +343,7 @@ func TestRemoveExtraRefs(t *testing.T) {
 			}
 			d := f.Dirent
 
-			if err := test.root.Remove(contexttest.Context(t), test.root, name); err != nil {
+			if err := test.root.Remove(contexttest.Context(t), test.root, name, false /* dirPath */); err != nil {
 				t.Fatalf("root.Remove(root, %q) failed: %v", name, err)
 			}
 

pkg/sentry/syscalls/linux/sys_file.go

@@ -1423,9 +1423,6 @@ func unlinkAt(t *kernel.Task, dirFD int32, addr usermem.Addr) error {
 	if err != nil {
 		return err
 	}
-	if dirPath {
-		return syserror.ENOENT
-	}
 
 	return fileOpAt(t, dirFD, path, func(root *fs.Dirent, d *fs.Dirent, name string, _ uint) error {
 		if !fs.IsDir(d.Inode.StableAttr) {
@@ -1436,7 +1433,7 @@ func unlinkAt(t *kernel.Task, dirFD int32, addr usermem.Addr) error {
 			return err
 		}
 
-		return d.Remove(t, root, name)
+		return d.Remove(t, root, name, dirPath)
 	})
 }
 

test/syscalls/linux/unlink.cc

@@ -123,6 +123,8 @@ TEST(UnlinkTest, AtBad) {
               SyscallSucceeds());
   EXPECT_THAT(unlinkat(dirfd, "UnlinkAtFile", AT_REMOVEDIR),
               SyscallFailsWithErrno(ENOTDIR));
+  EXPECT_THAT(unlinkat(dirfd, "UnlinkAtFile/", 0),
+              SyscallFailsWithErrno(ENOTDIR));
   ASSERT_THAT(close(fd), SyscallSucceeds());
   EXPECT_THAT(unlinkat(dirfd, "UnlinkAtFile", 0), SyscallSucceeds());