io_uring: fix mis-seting personality's creds

After io_identity_cow() copies an work.identity it wants to copy creds
to the new just allocated id, not the old one. Otherwise it's
akin to req->work.identity->creds = req->work.identity->creds.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -1284,7 +1284,7 @@ static bool io_identity_cow(struct io_kiocb *req)
 	 */
 	io_init_identity(id);
 	if (creds)
-		req->work.identity->creds = creds;
+		id->creds = creds;
 
 	/* add one for this request */
 	refcount_inc(&id->count);