ovl: port ovl_open_realfile() to cred guard

Use the scoped ovl cred guard.

Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-7-b31603935724@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 7ab2c9daffd0176b7a28f26ef790e5d37919a0a1..ebcd737e87ef14fe3ff5d0060d82992bef6beb15 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -31,7 +31,6 @@ static struct file *ovl_open_realfile(const struct file *file,
        struct inode *inode = file_inode(file);
        struct mnt_idmap *real_idmap;
        struct file *realfile;
-       const struct cred *old_cred;
        int flags = file->f_flags | OVL_OPEN_FLAGS;
        int acc_mode = ACC_MODE(flags);
        int err;
@@ -39,19 +38,19 @@ static struct file *ovl_open_realfile(const struct file *file,
        if (flags & O_APPEND)
                acc_mode |= MAY_APPEND;
 
-       old_cred = ovl_override_creds(inode->i_sb);
-       real_idmap = mnt_idmap(realpath->mnt);
-       err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
-       if (err) {
-               realfile = ERR_PTR(err);
-       } else {
-               if (!inode_owner_or_capable(real_idmap, realinode))
-                       flags &= ~O_NOATIME;
-
-               realfile = backing_file_open(file_user_path(file),
-                                            flags, realpath, current_cred());
+       with_ovl_creds(inode->i_sb) {
+               real_idmap = mnt_idmap(realpath->mnt);
+               err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
+               if (err) {
+                       realfile = ERR_PTR(err);
+               } else {
+                       if (!inode_owner_or_capable(real_idmap, realinode))
+                               flags &= ~O_NOATIME;
+
+                       realfile = backing_file_open(file_user_path(file),
+                                                    flags, realpath, current_cred());
+               }
        }
-       ovl_revert_creds(old_cred);
 
        pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
                 file, file, ovl_whatisit(inode, realinode), file->f_flags,