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=-17.0 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 3E88EC4361B for ; Sat, 19 Dec 2020 13:49:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E08D23B27 for ; Sat, 19 Dec 2020 13:49:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726630AbgLSNsr (ORCPT ); Sat, 19 Dec 2020 08:48:47 -0500 Received: from mail.kernel.org ([198.145.29.99]:35628 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726479AbgLSNsr (ORCPT ); Sat, 19 Dec 2020 08:48:47 -0500 From: Jeff Layton Authentication-Results: mail.kernel.org; dkim=permerror (bad message/signature format) To: viro@zeniv.linux.org.uk Cc: akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sargun@sargun.me, amir73il@gmail.com, vgoyal@redhat.com Subject: [PATCH][RESEND] vfs: protect file->f_sb_err with f_lock Date: Sat, 19 Dec 2020 08:48:04 -0500 Message-Id: <20201219134804.20034-1-jlayton@kernel.org> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When I added the ability for syncfs to report writeback errors, I neglected to adequately protect file->f_sb_err. We could have racing updates to that value if two tasks are issuing syncfs() on the same fd at the same time. Fix this by protecting the f_sb_err field with the file->f_lock, similarly to how the f_wb_err field is protected. Cc: stable@vger.kernel.org # v5.8+ Fixes: 735e4ae5ba28 (vfs: track per-sb writeback errors and report them to syncfs) Signed-off-by: Jeff Layton --- fs/sync.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) I sent this a couple of weeks ago, but no one picked it up. No changes from the original posting, but added the Fixes tag and marked it for stable. diff --git a/fs/sync.c b/fs/sync.c index 1373a610dc78..3be26ff72431 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -162,7 +162,7 @@ SYSCALL_DEFINE1(syncfs, int, fd) { struct fd f = fdget(fd); struct super_block *sb; - int ret, ret2; + int ret, ret2 = 0; if (!f.file) return -EBADF; @@ -172,7 +172,12 @@ SYSCALL_DEFINE1(syncfs, int, fd) ret = sync_filesystem(sb); up_read(&sb->s_umount); - ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); + if (errseq_check(&sb->s_wb_err, f.file->f_sb_err)) { + /* Something changed, must use slow path */ + spin_lock(&f.file->f_lock); + ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err); + spin_unlock(&f.file->f_lock); + } fdput(f); return ret ? ret : ret2; -- 2.29.2