From patchwork Mon Nov 4 02:05:42 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Long Li X-Patchwork-Id: 13860796 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9DAC6D1119B for ; Mon, 4 Nov 2024 02:09:32 +0000 (UTC) Received: from [127.0.0.1] (helo=sfs-ml-3.v29.lw.sourceforge.com) by sfs-ml-3.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1t7mX6-00011b-Da; Mon, 04 Nov 2024 02:09:31 +0000 Received: from [172.30.29.66] (helo=mx.sourceforge.net) by sfs-ml-3.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1t7mX4-00011U-9y for linux-f2fs-devel@lists.sourceforge.net; Mon, 04 Nov 2024 02:09:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Type:Content-Transfer-Encoding:MIME-Version :Message-ID:Date:Subject:CC:To:From:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=8C6M4Qs1e4lC9PXQb5bD3zaexPJqd5T4kiAWUIUkSO0=; b=U6UU1F6tp5Vh2YYcI4dLypntVX 9d7zWLnQvY8XeSZ73wr8iZKQHKiLzZ7+cL6wLXFJjhCj8apYawzMhW0qiDHWkWxJ+xf7gmr87Fa/i JQKiBeEJWHnVfv4n9uBj4D6dk4nW6Cj6+J73iYNUPBt6FG1PtV9glm/1WulX6ONM4ebM=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Type:Content-Transfer-Encoding:MIME-Version:Message-ID:Date: Subject:CC:To:From:Sender:Reply-To:Content-ID:Content-Description:Resent-Date :Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: References:List-Id:List-Help:List-Unsubscribe:List-Subscribe:List-Post: List-Owner:List-Archive; bh=8C6M4Qs1e4lC9PXQb5bD3zaexPJqd5T4kiAWUIUkSO0=; b=H GMtd/RdCrhs41DmQQbntyPuq2eRAhVJRUWdijWnjONZ3Ng1HVimUsvSAGEcZOWpsQdLZy3UDm/o08 A7qgNLabA9j6DrLoWQMqH9g5aN72KPPB6p/nu1bAPpQx5hFXbLZKtONbydBsCA4FkeQEEvFI035ca V9OesCUfzsjmliv4=; Received: from szxga07-in.huawei.com ([45.249.212.35]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1t7mX1-0000yV-AY for linux-f2fs-devel@lists.sourceforge.net; Mon, 04 Nov 2024 02:09:29 +0000 Received: from mail.maildlp.com (unknown [172.19.163.17]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4XhZc806H9z1SDqG; Mon, 4 Nov 2024 10:07:36 +0800 (CST) Received: from dggpemf500017.china.huawei.com (unknown [7.185.36.126]) by mail.maildlp.com (Postfix) with ESMTPS id A2A131A0188; Mon, 4 Nov 2024 10:09:14 +0800 (CST) Received: from huawei.com (10.175.104.67) by dggpemf500017.china.huawei.com (7.185.36.126) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 4 Nov 2024 10:09:14 +0800 To: , Date: Mon, 4 Nov 2024 10:05:42 +0800 Message-ID: <20241104020542.2603607-1-leo.lilong@huawei.com> X-Mailer: git-send-email 2.39.2 MIME-Version: 1.0 X-Originating-IP: [10.175.104.67] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemf500017.china.huawei.com (7.185.36.126) X-Headers-End: 1t7mX1-0000yV-AY Subject: [f2fs-dev] [PATCH v2] f2fs: fix race in concurrent f2fs_stop_gc_thread X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Long Li via Linux-f2fs-devel From: Long Li Reply-To: Long Li Cc: yi.zhang@huawei.com, lonuxli.64@gmail.com, yangerkun@huawei.com, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, leo.lilong@huawei.com Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net In my test case, concurrent calls to f2fs shutdown report the following stack trace: Oops: general protection fault, probably for non-canonical address 0xc6cfff63bb5513fc: 0000 [#1] PREEMPT SMP PTI CPU: 0 UID: 0 PID: 678 Comm: f2fs_rep_shutdo Not tainted 6.12.0-rc5-next-20241029-g6fb2fa9805c5-dirty #85 Call Trace: ? show_regs+0x8b/0xa0 ? __die_body+0x26/0xa0 ? die_addr+0x54/0x90 ? exc_general_protection+0x24b/0x5c0 ? asm_exc_general_protection+0x26/0x30 ? kthread_stop+0x46/0x390 f2fs_stop_gc_thread+0x6c/0x110 f2fs_do_shutdown+0x309/0x3a0 f2fs_ioc_shutdown+0x150/0x1c0 __f2fs_ioctl+0xffd/0x2ac0 f2fs_ioctl+0x76/0xe0 vfs_ioctl+0x23/0x60 __x64_sys_ioctl+0xce/0xf0 x64_sys_call+0x2b1b/0x4540 do_syscall_64+0xa7/0x240 entry_SYSCALL_64_after_hwframe+0x76/0x7e The root cause is a race condition in f2fs_stop_gc_thread() called from different f2fs shutdown paths: [CPU0] [CPU1] ---------------------- ----------------------- f2fs_stop_gc_thread f2fs_stop_gc_thread gc_th = sbi->gc_thread gc_th = sbi->gc_thread kfree(gc_th) sbi->gc_thread = NULL < gc_th != NULL > kthread_stop(gc_th->f2fs_gc_task) //UAF The commit c7f114d864ac ("f2fs: fix to avoid use-after-free in f2fs_stop_gc_thread()") attempted to fix this issue by using a read semaphore to prevent races between shutdown and remount threads, but it fails to prevent all race conditions. Fix it by converting to write lock of s_umount in f2fs_do_shutdown(). Fixes: 7950e9ac638e ("f2fs: stop gc/discard thread after fs shutdown") Signed-off-by: Long Li Reviewed-by: Chao Yu --- fs/f2fs/file.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 75a8b22da664..703cfccc6b7e 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -2365,9 +2365,12 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, if (readonly) goto out; - /* grab sb->s_umount to avoid racing w/ remount() */ + /* + * grab sb->s_umount to avoid racing w/ remount() and other shutdown + * paths. + */ if (need_lock) - down_read(&sbi->sb->s_umount); + down_write(&sbi->sb->s_umount); f2fs_stop_gc_thread(sbi); f2fs_stop_discard_thread(sbi); @@ -2376,7 +2379,7 @@ int f2fs_do_shutdown(struct f2fs_sb_info *sbi, unsigned int flag, clear_opt(sbi, DISCARD); if (need_lock) - up_read(&sbi->sb->s_umount); + up_write(&sbi->sb->s_umount); f2fs_update_time(sbi, REQ_TIME); out: