fusefrontend: fix chown on dangling symlinks

We (actually, go-fuse) used to call Chown() instead of Lchown()
which meant that the operation would fail on dangling symlinks.

Fix this by calling os.Lchown() ourself. Also add a test case
for this.

2 files changed, 18 insertions, 2 deletions

diff --git a/internal/fusefrontend/fs.go b/internal/fusefrontend/fs.go
index 988a41a..c216c86 100644
--- a/internal/fusefrontend/fs.go
+++ b/internal/fusefrontend/fs.go
@@ -165,11 +165,11 @@ func (fs *FS) Chown(path string, uid uint32, gid uint32, context *fuse.Context)
 	if fs.isFiltered(path) {
 		return fuse.EPERM
 	}
-	cPath, err := fs.encryptPath(path)
+	cPath, err := fs.getBackingPath(path)
 	if err != nil {
 		return fuse.ToStatus(err)
 	}
-	return fs.FileSystem.Chown(cPath, uid, gid, context)
+	return fuse.ToStatus(os.Lchown(cPath, int(uid), int(gid)))
 }
 
 func (fs *FS) Mknod(path string, mode uint32, dev uint32, context *fuse.Context) (code fuse.Status) {
diff --git a/tests/integration_tests/main_test.go b/tests/integration_tests/main_test.go
index b6cb8ca..17f9d9d 100644
--- a/tests/integration_tests/main_test.go
+++ b/tests/integration_tests/main_test.go
@@ -437,3 +437,19 @@ func TestLongNames(t *testing.T) {
 		t.Errorf("Leftover files, cnt1=%d cnt2=%d", cnt1, cnt2)
 	}
 }
+
+func TestLchown(t *testing.T) {
+	name := test_helpers.DefaultPlainDir + "symlink"
+	err := os.Symlink("/target/does/not/exist", name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	err = os.Chown(name, os.Getuid(), os.Getgid())
+	if err == nil {
+		t.Error("Chown on dangling symlink should fail")
+	}
+	err = os.Lchown(name, os.Getuid(), os.Getgid())
+	if err != nil {
+		t.Error(err)
+	}
+}