From: Christian Brauner <brauner@kernel.org>
Date: Mon, 17 Nov 2025 09:33:55 +0000 (+0100)
Subject: ovl: don't override credentials for ovl_check_whiteouts()
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=198d1822884a79e92a6e33284be90db5c09a48df;p=thirdparty%2Fkernel%2Flinux.git

ovl: don't override credentials for ovl_check_whiteouts()

The function is only called when rdd->dentry is non-NULL:

if (!err && rdd->first_maybe_whiteout && rdd->dentry)
    err = ovl_check_whiteouts(realpath, rdd);

| Caller                        | Sets rdd->dentry? | Can call ovl_check_whiteouts()? |
|-------------------------------|-------------------|---------------------------------|
| ovl_dir_read_merged()         | ✓ Yes (line 430)  | ✓ YES                           |
| ovl_dir_read_impure()         | ✗ No              | ✗ NO                            |
| ovl_check_d_type_supported()  | ✗ No              | ✗ NO                            |
| ovl_workdir_cleanup_recurse() | ✗ No              | ✗ NO                            |
| ovl_indexdir_cleanup()        | ✗ No              | ✗ NO                            |

VFS layer (.iterate_shared file operation)
  → ovl_iterate()
      [CRED OVERRIDE]
      → ovl_cache_get()
          → ovl_dir_read_merged()
              → ovl_dir_read()
                  → ovl_check_whiteouts()
      [CRED REVERT]

ovl_unlink()
  → ovl_do_remove()
      → ovl_check_empty_dir()
          [CRED OVERRIDE]
          → ovl_dir_read_merged()
              → ovl_dir_read()
                  → ovl_check_whiteouts()
          [CRED REVERT]

ovl_rename()
  → ovl_check_empty_dir()
      [CRED OVERRIDE]
      → ovl_dir_read_merged()
          → ovl_dir_read()
              → ovl_check_whiteouts()
      [CRED REVERT]

All valid callchains already override credentials so drop the override.

Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-24-b31603935724@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 77ecc39fc33af..2e345d39b1936 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -348,11 +348,7 @@ static bool ovl_fill_merge(struct dir_context *ctx, const char *name,
 
 static int ovl_check_whiteouts(const struct path *path, struct ovl_readdir_data *rdd)
 {
-	int err = 0;
 	struct dentry *dentry, *dir = path->dentry;
-	const struct cred *old_cred;
-
-	old_cred = ovl_override_creds(rdd->dentry->d_sb);
 
 	while (rdd->first_maybe_whiteout) {
 		struct ovl_cache_entry *p =
@@ -365,13 +361,11 @@ static int ovl_check_whiteouts(const struct path *path, struct ovl_readdir_data
 			p->is_whiteout = ovl_is_whiteout(dentry);
 			dput(dentry);
 		} else if (PTR_ERR(dentry) == -EINTR) {
-			err = -EINTR;
-			break;
+			return -EINTR;
 		}
 	}
-	ovl_revert_creds(old_cred);
 
-	return err;
+	return 0;
 }
 
 static inline int ovl_dir_read(const struct path *realpath,