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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 CD6B6C43464 for ; Fri, 18 Sep 2020 03:09:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84389206DB for ; Fri, 18 Sep 2020 03:09:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600398545; bh=vnqIYfPTu+rvfEetg3xuLYLSvU11yjq8XixlVaD1i4s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Zr7zUqd3t9Sx2pdlH1hy82v0d9Lseb7+WqiFwe/OkkFvrcPN0nznxCEGKUt45o+QF k+4YuZZsgXXuLVoviQzKC4RLeBraRSz8Q0BwcOJh3ss5qfSzrSH7OqP4RlfkA79bMt DBwxAmcT/1m6BsAzoTQnhFdET9Jv42N8SCBB2Kxw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727380AbgIRDI7 (ORCPT ); Thu, 17 Sep 2020 23:08:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:49174 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726980AbgIRCDM (ORCPT ); Thu, 17 Sep 2020 22:03:12 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 93D4221734; Fri, 18 Sep 2020 02:03:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1600394592; bh=vnqIYfPTu+rvfEetg3xuLYLSvU11yjq8XixlVaD1i4s=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wrkX60JnfaCHXY37mmMUy+iYSK0f29xgHjLKNRcD9uUlXWkPS3qiFVLZp3rwyLT9J KYlZa9YgVKeINsOqFQyMHvRE+OHuR27WLosoKwtk8xkIFm4JTwXFYve49HeqNjIS0j SZu+VOIR4KoDdIX/LpQmxufXENfa+8zYQDUwdv38= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Trond Myklebust , Trond Myklebust , "J . Bruce Fields" , Sasha Levin , linux-nfs@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 100/330] nfsd: Fix a soft lockup race in nfsd_file_mark_find_or_create() Date: Thu, 17 Sep 2020 21:57:20 -0400 Message-Id: <20200918020110.2063155-100-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200918020110.2063155-1-sashal@kernel.org> References: <20200918020110.2063155-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Trond Myklebust [ Upstream commit 90d2f1da832fd23290ef0c0d964d97501e5e8553 ] If nfsd_file_mark_find_or_create() keeps winning the race for the nfsd_file_fsnotify_group->mark_mutex against nfsd_file_mark_put() then it can soft lock up, since fsnotify_add_inode_mark() ends up always finding an existing entry. Signed-off-by: Trond Myklebust Signed-off-by: J. Bruce Fields Signed-off-by: Sasha Levin --- fs/nfsd/filecache.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 3007b8945d388..51c08ae79063c 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -133,9 +133,13 @@ nfsd_file_mark_find_or_create(struct nfsd_file *nf) struct nfsd_file_mark, nfm_mark)); mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex); - fsnotify_put_mark(mark); - if (likely(nfm)) + if (nfm) { + fsnotify_put_mark(mark); break; + } + /* Avoid soft lockup race with nfsd_file_mark_put() */ + fsnotify_destroy_mark(mark, nfsd_file_fsnotify_group); + fsnotify_put_mark(mark); } else mutex_unlock(&nfsd_file_fsnotify_group->mark_mutex); -- 2.25.1