[PATCH v2 09/16] overlayfs/dir: Convert to cred_guard()

[Vinicius Costa Gomes]

Replace the override_creds_light()/revert_creds_light() pairs of
operations with cred_guard()/cred_scoped_guard().

In ovl_do_remove(), cred_scoped_guard() was used because mixing
cred_guard() with 'goto' can cause the cleanup part of the guard to
run with garbage values.

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@xxxxxxxxx>
---
 fs/overlayfs/dir.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
index 52021e56b235..28ea6bc0a298 100644
--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -698,12 +698,10 @@ static int ovl_symlink(struct mnt_idmap *idmap, struct inode *dir,
 
 static int ovl_set_link_redirect(struct dentry *dentry)
 {
-	const struct cred *old_cred;
 	int err;
 
-	old_cred = ovl_override_creds_light(dentry->d_sb);
+	cred_guard(ovl_creds(dentry->d_sb));
 	err = ovl_set_redirect(dentry, false);
-	revert_creds_light(old_cred);
 
 	return err;
 }
@@ -889,7 +887,6 @@ static void ovl_drop_nlink(struct dentry *dentry)
 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 {
 	int err;
-	const struct cred *old_cred;
 	bool lower_positive = ovl_lower_positive(dentry);
 	LIST_HEAD(list);
 
@@ -908,12 +905,12 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 	if (err)
 		goto out;
 
-	old_cred = ovl_override_creds_light(dentry->d_sb);
-	if (!lower_positive)
-		err = ovl_remove_upper(dentry, is_dir, &list);
-	else
-		err = ovl_remove_and_whiteout(dentry, &list);
-	revert_creds_light(old_cred);
+	cred_scoped_guard(ovl_creds(dentry->d_sb)) {
+		if (!lower_positive)
+			err = ovl_remove_upper(dentry, is_dir, &list);
+		else
+			err = ovl_remove_and_whiteout(dentry, &list);
+	}
 	if (!err) {
 		if (is_dir)
 			clear_nlink(dentry->d_inode);
-- 
2.46.0