From patchwork Mon Feb 27 23:00:00 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kurz X-Patchwork-Id: 733219 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 3vXHkB2rf2z9s8X for ; Tue, 28 Feb 2017 10:20:18 +1100 (AEDT) Received: from localhost ([::1]:57527 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUaV-0000Du-FM for incoming@patchwork.ozlabs.org; Mon, 27 Feb 2017 18:20:15 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46829) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciUHk-0000Wp-1d for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciUHg-0003uF-N1 for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:52 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:55013) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ciUHg-0003sR-Cx for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:00:48 -0500 Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1RMraiH055656 for ; Mon, 27 Feb 2017 18:00:47 -0500 Received: from e06smtp08.uk.ibm.com (e06smtp08.uk.ibm.com [195.75.94.104]) by mx0a-001b2d01.pphosted.com with ESMTP id 28vq9ag95a-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 27 Feb 2017 18:00:47 -0500 Received: from localhost by e06smtp08.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 27 Feb 2017 23:00:44 -0000 Received: from d06dlp01.portsmouth.uk.ibm.com (9.149.20.13) by e06smtp08.uk.ibm.com (192.168.101.138) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; Mon, 27 Feb 2017 23:00:42 -0000 Received: from b06cxnps3075.portsmouth.uk.ibm.com (d06relay10.portsmouth.uk.ibm.com [9.149.109.195]) by d06dlp01.portsmouth.uk.ibm.com (Postfix) with ESMTP id 715DD17D8042; Mon, 27 Feb 2017 23:03:54 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (d06av23.portsmouth.uk.ibm.com [9.149.105.59]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v1RN0fkV17498602; Mon, 27 Feb 2017 23:00:41 GMT Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id C1CE1A404D; Mon, 27 Feb 2017 23:00:37 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 06C38A4040; Mon, 27 Feb 2017 23:00:37 +0000 (GMT) Received: from smtp.lab.toulouse-stg.fr.ibm.com (unknown [9.101.4.1]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 27 Feb 2017 23:00:36 +0000 (GMT) Received: from bahia.lan (icon-9-164-183-34.megacenter.de.ibm.com [9.164.183.34]) by smtp.lab.toulouse-stg.fr.ibm.com (Postfix) with ESMTP id E98FF220711; Tue, 28 Feb 2017 00:00:39 +0100 (CET) From: Greg Kurz To: qemu-devel@nongnu.org Date: Tue, 28 Feb 2017 00:00:00 +0100 X-Mailer: git-send-email 2.7.4 In-Reply-To: <1488236421-30983-1-git-send-email-groug@kaod.org> References: <1488236421-30983-1-git-send-email-groug@kaod.org> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17022723-0032-0000-0000-00000725B491 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17022723-0033-0000-0000-00002394EDB7 Message-Id: <1488236421-30983-11-git-send-email-groug@kaod.org> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-27_17:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=13 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702270213 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [generic] [fuzzy] X-Received-From: 148.163.156.1 Subject: [Qemu-devel] [PULL 10/31] 9pfs: local: lgetxattr: 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: Peter Maydell , "Aneesh Kumar K.V" , Greg Kurz Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" The local_lgetxattr() callback is vulnerable to symlink attacks because it calls lgetxattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fgetxattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lgetxattr(). local_lgetxattr() is converted to use this helper and opendir_nofollow(). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-posix-acl.c | 16 ++-------------- hw/9pfs/9p-util.c | 12 ++++++++++++ hw/9pfs/9p-util.h | 2 ++ hw/9pfs/9p-xattr-user.c | 8 +------- hw/9pfs/9p-xattr.c | 31 ++++++++++++++++++++++++------- hw/9pfs/9p-xattr.h | 2 ++ 6 files changed, 43 insertions(+), 28 deletions(-) diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c index ec003181cd33..9435e27a368c 100644 --- a/hw/9pfs/9p-posix-acl.c +++ b/hw/9pfs/9p-posix-acl.c @@ -25,13 +25,7 @@ static ssize_t mp_pacl_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, MAP_ACL_ACCESS, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size); } static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path, @@ -89,13 +83,7 @@ static int mp_pacl_removexattr(FsContext *ctx, static ssize_t mp_dacl_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, MAP_ACL_DEFAULT, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size); } static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path, diff --git a/hw/9pfs/9p-util.c b/hw/9pfs/9p-util.c index 4329a638cded..845b89439de7 100644 --- a/hw/9pfs/9p-util.c +++ b/hw/9pfs/9p-util.c @@ -11,6 +11,7 @@ */ #include "qemu/osdep.h" +#include "qemu/xattr.h" #include "9p-util.h" int relative_openat_nofollow(int dirfd, const char *path, int flags, @@ -54,3 +55,14 @@ int relative_openat_nofollow(int dirfd, const char *path, int flags, return fd; } + +ssize_t fgetxattrat_nofollow(int dirfd, const char *filename, const char *name, + void *value, size_t size) +{ + char *proc_path = g_strdup_printf("/proc/self/fd/%d/%s", dirfd, filename); + int ret; + + ret = lgetxattr(proc_path, name, value, size); + g_free(proc_path); + return ret; +} diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h index e3d5b66a15bc..806af82dcdbb 100644 --- a/hw/9pfs/9p-util.h +++ b/hw/9pfs/9p-util.h @@ -45,5 +45,7 @@ static inline int openat_file(int dirfd, const char *name, int flags, int relative_openat_nofollow(int dirfd, const char *path, int flags, mode_t mode); +ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name, + void *value, size_t size); #endif diff --git a/hw/9pfs/9p-xattr-user.c b/hw/9pfs/9p-xattr-user.c index f87530c8b526..4071fbc4c086 100644 --- a/hw/9pfs/9p-xattr-user.c +++ b/hw/9pfs/9p-xattr-user.c @@ -20,9 +20,6 @@ static ssize_t mp_user_getxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; - if (strncmp(name, "user.virtfs.", 12) == 0) { /* * Don't allow fetch of user.virtfs namesapce @@ -31,10 +28,7 @@ static ssize_t mp_user_getxattr(FsContext *ctx, const char *path, errno = ENOATTR; return -1; } - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, name, value, size); - g_free(buffer); - return ret; + return local_getxattr_nofollow(ctx, path, name, value, size); } static ssize_t mp_user_listxattr(FsContext *ctx, const char *path, diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c index 19a2daf02f5c..aa4391e6b317 100644 --- a/hw/9pfs/9p-xattr.c +++ b/hw/9pfs/9p-xattr.c @@ -15,6 +15,8 @@ #include "9p.h" #include "fsdev/file-op-9p.h" #include "9p-xattr.h" +#include "9p-util.h" +#include "9p-local.h" static XattrOperations *get_xattr_operations(XattrOperations **h, @@ -143,18 +145,33 @@ int v9fs_remove_xattr(FsContext *ctx, } -ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name, - void *value, size_t size) +ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size) { - char *buffer; - ssize_t ret; + char *dirpath = g_path_get_dirname(path); + char *filename = g_path_get_basename(path); + int dirfd; + ssize_t ret = -1; + + dirfd = local_opendir_nofollow(ctx, dirpath); + if (dirfd == -1) { + goto out; + } - buffer = rpath(ctx, path); - ret = lgetxattr(buffer, name, value, size); - g_free(buffer); + ret = fgetxattrat_nofollow(dirfd, filename, name, value, size); + close_preserve_errno(dirfd); +out: + g_free(dirpath); + g_free(filename); return ret; } +ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name, + void *value, size_t size) +{ + return local_getxattr_nofollow(ctx, path, name, value, size); +} + int pt_setxattr(FsContext *ctx, const char *path, const char *name, void *value, size_t size, int flags) { diff --git a/hw/9pfs/9p-xattr.h b/hw/9pfs/9p-xattr.h index 3f43f5153f3c..69a8b6b62e3c 100644 --- a/hw/9pfs/9p-xattr.h +++ b/hw/9pfs/9p-xattr.h @@ -29,6 +29,8 @@ typedef struct xattr_operations const char *path, const char *name); } XattrOperations; +ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path, + const char *name, void *value, size_t size); extern XattrOperations mapped_user_xattr; extern XattrOperations passthrough_user_xattr;