From nobody Wed May 8 19:22:37 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 (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1541710177678228.78473796501748; Thu, 8 Nov 2018 12:49:37 -0800 (PST) Received: from localhost ([::1]:58938 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gKrFA-0004de-K6 for importer@patchew.org; Thu, 08 Nov 2018 15:49:36 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53521) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gKrDE-0001Bi-KE for qemu-devel@nongnu.org; Thu, 08 Nov 2018 15:47:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gKr7c-0001eV-1S for qemu-devel@nongnu.org; Thu, 08 Nov 2018 15:41:51 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:41778 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gKr7b-0001UQ-IU for qemu-devel@nongnu.org; Thu, 08 Nov 2018 15:41:47 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id wA8Kd0WI009171 for ; Thu, 8 Nov 2018 15:41:36 -0500 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 2nmv4ngmh7-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 08 Nov 2018 15:41:36 -0500 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 8 Nov 2018 20:41:31 -0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id wA8KfUHO50004064 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 8 Nov 2018 20:41:31 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id CA1BB11C054; Thu, 8 Nov 2018 20:41:30 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B698511C050; Thu, 8 Nov 2018 20:41:30 +0000 (GMT) Received: from smtp.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.1]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 8 Nov 2018 20:41:30 +0000 (GMT) Received: from bahia.ibmmodules.com (sig-9-145-157-123.de.ibm.com [9.145.157.123]) by smtp.lab.toulouse-stg.fr.ibm.com (Postfix) with ESMTP id 33AC8220075; Thu, 8 Nov 2018 21:41:30 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Thu, 8 Nov 2018 21:41:10 +0100 X-Mailer: git-send-email 2.17.2 In-Reply-To: <20181108204111.786455-1-groug@kaod.org> References: <20181108204111.786455-1-groug@kaod.org> X-TM-AS-GCONF: 00 x-cbid: 18110820-0016-0000-0000-0000022405BC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18110820-0017-0000-0000-0000327C05E8 Message-Id: <20181108204111.786455-2-groug@kaod.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2018-11-08_11:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=13 phishscore=0 bulkscore=0 spamscore=0 clxscore=1034 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=835 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1811080175 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PULL 1/1] 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: Peter Maydell , Greg Kurz , P J P Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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, --=20 2.17.2