cifs: avoid pointless cred reference count bump

During module init root_cred will be allocated with its own reference
which is only destroyed during module exit.

Link: https://lore.kernel.org/r/20241125-work-cred-v2-20-68b9d38bb5b2@kernel.org
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/smb/client/cifsacl.c

@@ -292,7 +292,7 @@ id_to_sid(unsigned int cid, uint sidtype, struct smb_sid *ssid)
 		return -EINVAL;
 
 	rc = 0;
-	saved_cred = override_creds(get_new_cred(root_cred));
+	saved_cred = override_creds(root_cred);
 	sidkey = request_key(&cifs_idmap_key_type, desc, "");
 	if (IS_ERR(sidkey)) {
 		rc = -EINVAL;
@@ -327,7 +327,7 @@ id_to_sid(unsigned int cid, uint sidtype, struct smb_sid *ssid)
 out_key_put:
 	key_put(sidkey);
 out_revert_creds:
-	put_cred(revert_creds(saved_cred));
+	revert_creds(saved_cred);
 	return rc;
 
 invalidate_key:
@@ -398,7 +398,7 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct smb_sid *psid,
 	if (!sidstr)
 		return -ENOMEM;
 
-	saved_cred = override_creds(get_new_cred(root_cred));
+	saved_cred = override_creds(root_cred);
 	sidkey = request_key(&cifs_idmap_key_type, sidstr, "");
 	if (IS_ERR(sidkey)) {
 		cifs_dbg(FYI, "%s: Can't map SID %s to a %cid\n",
@@ -438,7 +438,7 @@ sid_to_id(struct cifs_sb_info *cifs_sb, struct smb_sid *psid,
 out_key_put:
 	key_put(sidkey);
 out_revert_creds:
-	put_cred(revert_creds(saved_cred));
+	revert_creds(saved_cred);
 	kfree(sidstr);
 
 	/*