From patchwork Fri May 13 14:23:37 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 572942 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D035C433EF for ; Fri, 13 May 2022 14:27:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357833AbiEMO1L (ORCPT ); Fri, 13 May 2022 10:27:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380942AbiEMO0S (ORCPT ); Fri, 13 May 2022 10:26:18 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 49B385F8E2; Fri, 13 May 2022 07:25:54 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id C9B77B8306F; Fri, 13 May 2022 14:25:52 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2E01DC34100; Fri, 13 May 2022 14:25:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1652451951; bh=3ZAQoHJRAorjhE63N9J2GNWT/DBzxa637Mj9/BzDMmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0OYEq3/QdjkmG/2dCQbjMUeid3PUAGUqPfPzllHHeRGsG34HaQLb95evAKkMBYbRA l0aJm3leAmUAD5rSUaw/9cxSudi50uCsFM2KFwPe7pujExcFJMQE0XJ6EtC5P1HNsG /5ETxIG67ZNgjTrChv7dXY0vkiKjzcNRLUesKveQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, David Howells , ChenXiaoSong Subject: [PATCH 4.19 15/15] VFS: Fix memory leak caused by concurrently mounting fs with subtype Date: Fri, 13 May 2022 16:23:37 +0200 Message-Id: <20220513142228.347780404@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220513142227.897535454@linuxfoundation.org> References: <20220513142227.897535454@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: ChenXiaoSong If two processes mount same superblock, memory leak occurs: CPU0 | CPU1 do_new_mount | do_new_mount fs_set_subtype | fs_set_subtype kstrdup | | kstrdup memrory leak | The following reproducer triggers the problem: 1. shell command: mount -t ntfs /dev/sda1 /mnt & 2. c program: mount("/dev/sda1", "/mnt", "fuseblk", 0, "...") with kmemleak report being along the lines of unreferenced object 0xffff888235f1a5c0 (size 8): comm "mount.ntfs", pid 2860, jiffies 4295757824 (age 43.423s) hex dump (first 8 bytes): 00 a5 f1 35 82 88 ff ff ...5.... backtrace: [<00000000656e30cc>] __kmalloc_track_caller+0x16e/0x430 [<000000008e591727>] kstrdup+0x3e/0x90 [<000000008430d12b>] do_mount.cold+0x7b/0xd9 [<0000000078d639cd>] ksys_mount+0xb2/0x150 [<000000006015988d>] __x64_sys_mount+0x29/0x40 [<00000000e0a7c118>] do_syscall_64+0xc1/0x1d0 [<00000000bcea7df5>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [<00000000803a4067>] 0xffffffffffffffff Linus's tree already have refactoring patchset [1], one of them can fix this bug: c30da2e981a7 ("fuse: convert to use the new mount API") After refactoring, init super_block->s_subtype in fuse_fill_super. Since we did not merge the refactoring patchset in this branch, I create this patch. This patch fix this by adding a write lock while calling fs_set_subtype. [1] https://patchwork.kernel.org/project/linux-fsdevel/patch/20190903113640.7984-3-mszeredi@redhat.com/ Fixes: 79c0b2df79eb ("add filesystem subtype support") Cc: David Howells Cc: Signed-off-by: ChenXiaoSong Signed-off-by: Greg Kroah-Hartman --- v1: Can not mount sshfs ([PATCH linux-4.19.y] VFS: Fix fuseblk memory leak caused by mount concurrency) v2: Use write lock while writing superblock ([PATCH 4.19,v2] VFS: Fix fuseblk memory leak caused by mount concurrency) v3: Update commit message fs/namespace.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2490,9 +2490,12 @@ static int do_new_mount(struct path *pat return -ENODEV; mnt = vfs_kern_mount(type, sb_flags, name, data); - if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && - !mnt->mnt_sb->s_subtype) - mnt = fs_set_subtype(mnt, fstype); + if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE)) { + down_write(&mnt->mnt_sb->s_umount); + if (!mnt->mnt_sb->s_subtype) + mnt = fs_set_subtype(mnt, fstype); + up_write(&mnt->mnt_sb->s_umount); + } put_filesystem(type); if (IS_ERR(mnt))