From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F97AC433E6 for ; Tue, 1 Sep 2020 03:19:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3DDDE20719 for ; Tue, 1 Sep 2020 03:19:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726044AbgIADTv (ORCPT ); Mon, 31 Aug 2020 23:19:51 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725987AbgIADTu (ORCPT ); Mon, 31 Aug 2020 23:19:50 -0400 Received: from ZenIV.linux.org.uk (zeniv.linux.org.uk [IPv6:2002:c35c:fd02::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CC8CC061366; Mon, 31 Aug 2020 20:19:50 -0700 (PDT) Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kCwpl-008RqV-Sx; Tue, 01 Sep 2020 03:19:45 +0000 Date: Tue, 1 Sep 2020 04:19:45 +0100 From: Al Viro To: Hillf Danton Cc: syzbot , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, maz@kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: KASAN: use-after-free Read in __fput (3) Message-ID: <20200901031945.GE1236603@ZenIV.linux.org.uk> References: <000000000000438ab305ae347ac4@google.com> <20200901023547.14976-1-hdanton@sina.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200901023547.14976-1-hdanton@sina.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Tue, Sep 01, 2020 at 10:35:47AM +0800, Hillf Danton wrote: > Any light on how a9ed4a6560b8 ends up with __fput called twice is > highly appreciated. diff --git a/fs/eventpoll.c b/fs/eventpoll.c index e0decff22ae2..8107e06d7f6f 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1995,9 +1995,9 @@ static int ep_loop_check_proc(void *priv, void *cookie, int call_nests) * during ep_insert(). */ if (list_empty(&epi->ffd.file->f_tfile_llink)) { - get_file(epi->ffd.file); - list_add(&epi->ffd.file->f_tfile_llink, - &tfile_check_list); + if (get_file_rcu(epi->ffd.file)) + list_add(&epi->ffd.file->f_tfile_llink, + &tfile_check_list); } } }