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=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 CBF66C4727F for ; Tue, 29 Sep 2020 12:42:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BDDD208B8 for ; Tue, 29 Sep 2020 12:42:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601383355; bh=sTH9H5cLkDDkeT7+8BSnxFuTL3G71zT6DoZ7bdCP3GE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=11F1qfe6d/ozwl1JVPCD0JRVFV0QfJ2UcczAeiaxOBTMUH6DpeXO8jA23GEx+jdiD vtBBCgL4GNOTmTpF6tQ1ao0Gj/pA5PmhupR0hfMJH8SoQZlbSkGYa4bmV6DsV1loWO cDfnVCi6MtDBPwz2x9Hbn5hOhiLZNPSouC1Yll2c= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728921AbgI2LL2 (ORCPT ); Tue, 29 Sep 2020 07:11:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:51946 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729194AbgI2LKw (ORCPT ); Tue, 29 Sep 2020 07:10:52 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9628720848; Tue, 29 Sep 2020 11:10:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601377852; bh=sTH9H5cLkDDkeT7+8BSnxFuTL3G71zT6DoZ7bdCP3GE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G2l5qnXiRXoc4dmM7a02nJ4Ar8W+17SuF6gouRZ+uIu4QhrvUci4B11CmDp/xx3Yd D32k3gMZ3RzKw9KIx8A0Q2zGTwmQmcIb8wrTcQHVxEZMKycCFafU1qi11aFoHaahim 8/A/P0TBVOznPkOCV2Dze9D6As21YJeDMFRbcjhI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jeff Layton , Ilya Dryomov , Sasha Levin Subject: [PATCH 4.9 096/121] ceph: fix potential race in ceph_check_caps Date: Tue, 29 Sep 2020 13:00:40 +0200 Message-Id: <20200929105934.940310959@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105930.172747117@linuxfoundation.org> References: <20200929105930.172747117@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jeff Layton [ Upstream commit dc3da0461cc4b76f2d0c5b12247fcb3b520edbbf ] Nothing ensures that session will still be valid by the time we dereference the pointer. Take and put a reference. In principle, we should always be able to get a reference here, but throw a warning if that's ever not the case. Signed-off-by: Jeff Layton Signed-off-by: Ilya Dryomov Signed-off-by: Sasha Levin --- fs/ceph/caps.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index e11aacb35d6b5..cbd92dd89de16 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1807,12 +1807,24 @@ ack: if (mutex_trylock(&session->s_mutex) == 0) { dout("inverting session/ino locks on %p\n", session); + session = ceph_get_mds_session(session); spin_unlock(&ci->i_ceph_lock); if (took_snap_rwsem) { up_read(&mdsc->snap_rwsem); took_snap_rwsem = 0; } - mutex_lock(&session->s_mutex); + if (session) { + mutex_lock(&session->s_mutex); + ceph_put_mds_session(session); + } else { + /* + * Because we take the reference while + * holding the i_ceph_lock, it should + * never be NULL. Throw a warning if it + * ever is. + */ + WARN_ON_ONCE(true); + } goto retry; } } -- 2.25.1