From nobody Wed May 15 19:54:29 2024 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (208.118.235.17 [208.118.235.17]) by mx.zohomail.com with SMTPS id 1541550898677277.15059116171756; Tue, 6 Nov 2018 16:34:58 -0800 (PST) Received: from localhost ([::1]:44989 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gKBo4-0000DB-N8 for importer@patchew.org; Tue, 06 Nov 2018 19:34:52 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40563) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gKBmC-0005tx-Di for qemu-devel@nongnu.org; Tue, 06 Nov 2018 19:33:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gKBbP-0004cX-Ji for qemu-devel@nongnu.org; Tue, 06 Nov 2018 19:21:50 -0500 Received: from 17.mo1.mail-out.ovh.net ([87.98.179.142]:48014) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gKBbN-0002fF-BT for qemu-devel@nongnu.org; Tue, 06 Nov 2018 19:21:47 -0500 Received: from player157.ha.ovh.net (unknown [10.109.159.73]) by mo1.mail-out.ovh.net (Postfix) with ESMTP id 985C7141772 for ; Wed, 7 Nov 2018 01:21:22 +0100 (CET) Received: from kaod.org (lns-bzn-46-82-253-208-248.adsl.proxad.net [82.253.208.248]) (Authenticated sender: groug@kaod.org) by player157.ha.ovh.net (Postfix) with ESMTPSA id 35CC7100077; Wed, 7 Nov 2018 01:21:19 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Wed, 07 Nov 2018 01:21:18 +0100 Message-ID: <154155007870.439125.16160474206652257208.stgit@bahia.lan> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Ovh-Tracer-Id: 3459327465536002368 X-VR-SPAMSTATE: OK X-VR-SPAMSCORE: -100 X-VR-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedtkedrjeekgddvudcutefuodetggdotefrodftvfcurfhrohhfihhlvgemucfqggfjpdevjffgvefmvefgnecuuegrihhlohhuthemucehtddtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmd X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 87.98.179.142 Subject: [Qemu-devel] [PATCH] 9p: write lock path in v9fs_co_open2() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Prasad J Pandit , Greg Kurz , zhibin hu Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" The assumption that the fid cannot be used by any other operation is wrong. At least, nothing prevents a misbehaving client to create a file with a given fid, and to pass this fid to some other operation at the same time (ie, without waiting for the response to the creation request). The call to v9fs_path_copy() performed by the worker thread after the file was created can race with any access to the fid path performed by some other thread. This causes use-after-free issues that can be detected by ASAN with a custom 9p client. Unlike other operations that only read the fid path, v9fs_co_open2() does modify it. It should hence take the write lock. Cc: P J P Reported-by: zhibin hu Signed-off-by: Greg Kurz --- hw/9pfs/cofile.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/hw/9pfs/cofile.c b/hw/9pfs/cofile.c index 88791bc327ac..9c22837cda32 100644 --- a/hw/9pfs/cofile.c +++ b/hw/9pfs/cofile.c @@ -140,10 +140,10 @@ int coroutine_fn v9fs_co_open2(V9fsPDU *pdu, V9fsFidS= tate *fidp, cred.fc_gid =3D gid; /* * Hold the directory fid lock so that directory path name - * don't change. Read lock is fine because this fid cannot - * be used by any other operation. + * don't change. Take the write lock to be sure this fid + * cannot be used by another operation. */ - v9fs_path_read_lock(s); + v9fs_path_write_lock(s); v9fs_co_run_in_worker( { err =3D s->ops->open2(&s->ctx, &fidp->path,