Merge patch series "ovl: convert to cred guard"

Christian Brauner <brauner@kernel.org> says:

This adds an overlayfs specific extension of the cred guard
infrastructure I introduced. This allows all of overlayfs to be ported
to cred guards. I refactored a few functions to reduce the scope of the
cred guard. I think this is beneficial as it's visually very easy to
grasp the scope in one go. Lightly tested.

* patches from https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-0-b31603935724@kernel.org: (42 commits)
  ovl: remove ovl_revert_creds()
  ovl: port ovl_fill_super() to cred guard
  ovl: refactor ovl_fill_super()
  ovl: port ovl_lower_positive() to cred guard
  ovl: port ovl_lookup() to cred guard
  ovl: refactor ovl_lookup()
  ovl: port ovl_copyfile() to cred guard
  ovl: port ovl_rename() to cred guard
  ovl: refactor ovl_rename()
  ovl: introduce struct ovl_renamedata
  ovl: port ovl_listxattr() to cred guard
  ovl: port ovl_xattr_get() to cred guard
  ovl: port ovl_xattr_set() to cred guard
  ovl: port ovl_nlink_end() to cred guard
  ovl: port ovl_nlink_start() to cred guard
  ovl: port ovl_check_empty_dir() to cred guard
  ovl: port ovl_dir_llseek() to cred guard
  ovl: refactor ovl_iterate() and port to cred guard
  ovl: don't override credentials for ovl_check_whiteouts()
  ovl: port ovl_maybe_lookup_lowerdata() to cred guard
  ...

Link: https://patch.msgid.link/20251117-work-ovl-cred-guard-v4-0-b31603935724@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/overlayfs/copy_up.c

@@ -1203,7 +1203,6 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 static int ovl_copy_up_flags(struct dentry *dentry, int flags)
 {
 	int err = 0;
-	const struct cred *old_cred;
 	bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);
 
 	/*
@@ -1223,7 +1222,6 @@ static int ovl_copy_up_flags(struct dentry *dentry, int flags)
 	if (err)
 		return err;
 
-	old_cred = ovl_override_creds(dentry->d_sb);
 	while (!err) {
 		struct dentry *next;
 		struct dentry *parent = NULL;
@@ -1243,12 +1241,12 @@ static int ovl_copy_up_flags(struct dentry *dentry, int flags)
 			next = parent;
 		}
 
-		err = ovl_copy_up_one(parent, next, flags);
+		with_ovl_creds(dentry->d_sb)
+			err = ovl_copy_up_one(parent, next, flags);
 
 		dput(parent);
 		dput(next);
 	}
-	ovl_revert_creds(old_cred);
 
 	return err;
 }