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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 80637C07E9C for ; Mon, 5 Jul 2021 10:52:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 60C626100B for ; Mon, 5 Jul 2021 10:52:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231186AbhGEKzV (ORCPT ); Mon, 5 Jul 2021 06:55:21 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:54866 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230511AbhGEKzT (ORCPT ); Mon, 5 Jul 2021 06:55:19 -0400 Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 350D01FE5A; Mon, 5 Jul 2021 10:52:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1625482362; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Fpm40tJrF9OSlPlTcqcUfpdONlePzhoBnOab2uQUEys=; b=0wEkN24gF/FOmZ1iPTXdKv+M4eUgo2mxXHZhcFd6bxgAwW6i8jEqxLhyej7PVorl3ws5gI FKmxyKr9K9VyjYWH+xAO0BU9RXCEl1wZOMOQocztIWk3USjI50tBTyfTRccTJBFWwWISzE bhSY4u1lGl3Fmp8jNzbyw+OOhkvG8Jo= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1625482362; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Fpm40tJrF9OSlPlTcqcUfpdONlePzhoBnOab2uQUEys=; b=UOBQlRxLr7p1DxkwBpr202hhGJvFbA3oe6t9Na57yO3DPeRaKbY1AZlPcIrbUwlGguOhwn Ti6GeTi9N5Co7dCw== Received: from quack2.suse.cz (unknown [10.163.43.118]) by relay2.suse.de (Postfix) with ESMTP id 25638A3B8A; Mon, 5 Jul 2021 10:52:42 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id EAFB81E1139; Mon, 5 Jul 2021 12:52:41 +0200 (CEST) Date: Mon, 5 Jul 2021 12:52:41 +0200 From: Jan Kara To: Ye Bin Cc: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, jack@suse.cz Subject: Re: [PATCH 2/2] ext4: Fix potential uas-after-free about sbi->s_mmp_tsk when kmmpd kthread exit before set sbi->s_mmp_tsk Message-ID: <20210705105241.GC15373@quack2.suse.cz> References: <20210629143603.2166962-1-yebin10@huawei.com> <20210629143603.2166962-3-yebin10@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210629143603.2166962-3-yebin10@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 29-06-21 22:36:03, Ye Bin wrote: > Now sbi->s_mmp_tsk is created with kthread_run, then kmmpd maybe > already running and even exit as exception. Even though we set > sbi->s_mmp_tsk with NULL before kmmpd kthread exit, but > "sbi->s_mmp_tsk=kthread_run(XX)" may set after set with NULL. > mount kmmpd > | | > |-call kthread_run | > | |-kmmpd runing > | |-kmmpd exit sbi->s_mmp_tsk=NULL > | | > |-kthread_run return | > | and set sbi->s_mmp_tsk | > | | > |-then we get wild ptr"sbi->s_mmp_tsk" and later trigger UAF > > This patch is base on previous "ext4: Fix use-after-free about sbi->s_mmp_tsk". > Previous patch ensure kmmpd kthread exit by itself will set sbi->s_mmp_tsk with > NULL. We can create kthread first, and then wakeup kmmpd kthread later. > > Signed-off-by: Ye Bin Looks good. Feel free to add: Reviewed-by: Jan Kara Honza > --- > fs/ext4/mmp.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/fs/ext4/mmp.c b/fs/ext4/mmp.c > index fc18a8c205c7..6ec1ea182cc0 100644 > --- a/fs/ext4/mmp.c > +++ b/fs/ext4/mmp.c > @@ -394,16 +394,18 @@ int ext4_multi_mount_protect(struct super_block *sb, > /* > * Start a kernel thread to update the MMP block periodically. > */ > - EXT4_SB(sb)->s_mmp_tsk = kthread_run(kmmpd, sb, "kmmpd-%.*s", > - (int)sizeof(mmp->mmp_bdevname), > - bdevname(bh->b_bdev, > - mmp->mmp_bdevname)); > + EXT4_SB(sb)->s_mmp_tsk = kthread_create(kmmpd, sb, "kmmpd-%.*s", > + (int)sizeof(mmp->mmp_bdevname), > + bdevname(bh->b_bdev, > + mmp->mmp_bdevname)); > + > if (IS_ERR(EXT4_SB(sb)->s_mmp_tsk)) { > EXT4_SB(sb)->s_mmp_tsk = NULL; > ext4_warning(sb, "Unable to create kmmpd thread for %s.", > sb->s_id); > goto failed; > } > + wake_up_process(EXT4_SB(sb)->s_mmp_tsk); > > return 0; > > -- > 2.31.1 > -- Jan Kara SUSE Labs, CR