From nobody Mon Feb 9 10:21:58 2026 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.zoho.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 1488149834667776.4281473090653; Sun, 26 Feb 2017 14:57:14 -0800 (PST) Received: from localhost ([::1]:48810 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7kf-0000j1-Fp for importer@patchew.org; Sun, 26 Feb 2017 17:57:13 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50593) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ci7Wx-0005Mx-NW for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ci7Wu-0002s1-If for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:03 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:50679 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 1ci7Wu-0002rv-BD for qemu-devel@nongnu.org; Sun, 26 Feb 2017 17:43:00 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1QMcRkP086543 for ; Sun, 26 Feb 2017 17:42:59 -0500 Received: from e33.co.us.ibm.com (e33.co.us.ibm.com [32.97.110.151]) by mx0a-001b2d01.pphosted.com with ESMTP id 28u862td31-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sun, 26 Feb 2017 17:42:59 -0500 Received: from localhost by e33.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; Sun, 26 Feb 2017 15:42:55 -0700 Received: from b03cxnp07029.gho.boulder.ibm.com (b03cxnp07029.gho.boulder.ibm.com [9.17.130.16]) by d03dlp02.boulder.ibm.com (Postfix) with ESMTP id 26B503E40030; Sun, 26 Feb 2017 15:42:55 -0700 (MST) Received: from b03ledav004.gho.boulder.ibm.com (b03ledav004.gho.boulder.ibm.com [9.17.130.235]) by b03cxnp07029.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1QMgtTu15925568; Sun, 26 Feb 2017 15:42:55 -0700 Received: from b03ledav004.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0319478038; Sun, 26 Feb 2017 15:42:55 -0700 (MST) Received: from [192.168.66.23] (unknown [9.164.183.34]) by b03ledav004.gho.boulder.ibm.com (Postfix) with ESMTP id 50C1178037; Sun, 26 Feb 2017 15:42:53 -0700 (MST) From: Greg Kurz To: qemu-devel@nongnu.org Date: Sun, 26 Feb 2017 23:42:51 +0100 In-Reply-To: <148814889214.28146.16915712763478774662.stgit@bahia> References: <148814889214.28146.16915712763478774662.stgit@bahia> User-Agent: StGit/0.17.1-20-gc0b1b-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022622-0008-0000-0000-000007568D7C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006689; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000204; SDB=6.00827424; UDB=6.00405424; IPR=6.00604940; BA=6.00005172; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014449; XFM=3.00000011; UTC=2017-02-26 22:42:57 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022622-0009-0000-0000-0000403E7705 Message-Id: <148814897182.28146.16499801111559710291.stgit@bahia> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-26_11:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=3 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702260233 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.158.5 Subject: [Qemu-devel] [PATCH v2 10/28] 9pfs: local: lremovexattr: don't follow symlinks 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: Jann Horn , Prasad J Pandit , Greg Kurz , "Aneesh Kumar K.V" , Stefan Hajnoczi Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 The local_lremovexattr() callback is vulnerable to symlink attacks because it calls lremovexattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fremovexattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lremovexattr(). local_lremovexattr() is converted to use this helper and opendir_nofollow(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- v2: - introduce /proc based fremovexattrat_nofollow() - fix arguments passed to local_removexattr_nofollow() --- hw/9pfs/9p-posix-acl.c | 10 ++-------- hw/9pfs/9p-xattr-user.c | 8 +------- hw/9pfs/9p-xattr.c | 36 +++++++++++++++++++++++++++++++----- hw/9pfs/9p-xattr.h | 2 ++ 4 files changed, 36 insertions(+), 20 deletions(-) diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c index 0154e2a7605f..bbf89064f7ae 100644 --- a/hw/9pfs/9p-posix-acl.c +++ b/hw/9pfs/9p-posix-acl.c @@ -58,10 +58,8 @@ static int mp_pacl_removexattr(FsContext *ctx, const char *path, const char *name) { int ret; - char *buffer; =20 - buffer =3D rpath(ctx, path); - ret =3D lremovexattr(buffer, MAP_ACL_ACCESS); + ret =3D local_removexattr_nofollow(ctx, path, MAP_ACL_ACCESS); if (ret =3D=3D -1 && errno =3D=3D ENODATA) { /* * We don't get ENODATA error when trying to remove a @@ -71,7 +69,6 @@ static int mp_pacl_removexattr(FsContext *ctx, errno =3D 0; ret =3D 0; } - g_free(buffer); return ret; } =20 @@ -111,10 +108,8 @@ static int mp_dacl_removexattr(FsContext *ctx, const char *path, const char *name) { int ret; - char *buffer; =20 - buffer =3D rpath(ctx, path); - ret =3D lremovexattr(buffer, MAP_ACL_DEFAULT); + ret =3D local_removexattr_nofollow(ctx, path, MAP_ACL_DEFAULT); if (ret =3D=3D -1 && errno =3D=3D ENODATA) { /* * We don't get ENODATA error when trying to remove a @@ -124,7 +119,6 @@ static int mp_dacl_removexattr(FsContext *ctx, errno =3D 0; ret =3D 0; } - g_free(buffer); return ret; } =20 diff --git a/hw/9pfs/9p-xattr-user.c b/hw/9pfs/9p-xattr-user.c index 1840a5db66f3..2c90817b75a6 100644 --- a/hw/9pfs/9p-xattr-user.c +++ b/hw/9pfs/9p-xattr-user.c @@ -81,9 +81,6 @@ static int mp_user_setxattr(FsContext *ctx, const char *p= ath, const char *name, static int mp_user_removexattr(FsContext *ctx, const char *path, const char *name) { - char *buffer; - int ret; - if (strncmp(name, "user.virtfs.", 12) =3D=3D 0) { /* * Don't allow fetch of user.virtfs namesapce @@ -92,10 +89,7 @@ static int mp_user_removexattr(FsContext *ctx, errno =3D EACCES; return -1; } - buffer =3D rpath(ctx, path); - ret =3D lremovexattr(buffer, name); - g_free(buffer); - return ret; + return local_removexattr_nofollow(ctx, path, name); } =20 XattrOperations mapped_user_xattr =3D { diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c index a0167dd4d898..eec160b3c2ac 100644 --- a/hw/9pfs/9p-xattr.c +++ b/hw/9pfs/9p-xattr.c @@ -234,17 +234,43 @@ int pt_setxattr(FsContext *ctx, const char *path, con= st char *name, void *value, return local_setxattr_nofollow(ctx, path, name, value, size, flags); } =20 -int pt_removexattr(FsContext *ctx, const char *path, const char *name) +static ssize_t fremovexattrat_nofollow(int dirfd, const char *filename, + const char *name) { - char *buffer; + char *proc_path =3D g_strdup_printf("/proc/self/fd/%d/%s", dirfd, file= name); int ret; =20 - buffer =3D rpath(ctx, path); - ret =3D lremovexattr(path, name); - g_free(buffer); + ret =3D lremovexattr(proc_path, name); + g_free(proc_path); return ret; } =20 +ssize_t local_removexattr_nofollow(FsContext *ctx, const char *path, + const char *name) +{ + char *dirpath =3D g_path_get_dirname(path); + char *filename =3D g_path_get_basename(path); + int dirfd; + ssize_t ret =3D -1; + + dirfd =3D local_opendir_nofollow(ctx, dirpath); + if (dirfd =3D=3D -1) { + goto out; + } + + ret =3D fremovexattrat_nofollow(dirfd, filename, name); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(filename); + return ret; +} + +int pt_removexattr(FsContext *ctx, const char *path, const char *name) +{ + return local_removexattr_nofollow(ctx, path, name); +} + ssize_t notsup_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { diff --git a/hw/9pfs/9p-xattr.h b/hw/9pfs/9p-xattr.h index 7558970d8511..0d83996575e1 100644 --- a/hw/9pfs/9p-xattr.h +++ b/hw/9pfs/9p-xattr.h @@ -34,6 +34,8 @@ ssize_t local_getxattr_nofollow(FsContext *ctx, const cha= r *path, ssize_t local_setxattr_nofollow(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags); +ssize_t local_removexattr_nofollow(FsContext *ctx, const char *path, + const char *name); =20 extern XattrOperations mapped_user_xattr; extern XattrOperations passthrough_user_xattr;