From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37585) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cif3f-0001Ci-Ew for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:04 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cif3c-0007wl-1d for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:03 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:35060 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 1cif3b-0007va-JG for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:30:59 -0500 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1SATE5h093636 for ; Tue, 28 Feb 2017 05:30:58 -0500 Received: from e06smtp12.uk.ibm.com (e06smtp12.uk.ibm.com [195.75.94.108]) by mx0b-001b2d01.pphosted.com with ESMTP id 28w28kny5v-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 28 Feb 2017 05:30:58 -0500 Received: from localhost by e06smtp12.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 28 Feb 2017 10:30:57 -0000 From: Greg Kurz Date: Tue, 28 Feb 2017 11:30:18 +0100 In-Reply-To: <1488277840-18608-1-git-send-email-groug@kaod.org> References: <1488277840-18608-1-git-send-email-groug@kaod.org> Message-Id: <1488277840-18608-7-git-send-email-groug@kaod.org> Subject: [Qemu-devel] [PULL 06/28] 9pfs: local: open/opendir: don't follow symlinks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Peter Maydell , "Aneesh Kumar K.V" , Greg Kurz The local_open() and local_opendir() callbacks are vulnerable to symlink attacks because they call: (1) open(O_NOFOLLOW) which follows symbolic links in all path elements but the rightmost one (2) opendir() which follows symbolic links in all path elements This patch converts both callbacks to use new helpers based on openat_nofollow() to only open files and directories if they are below the virtfs shared folder This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 37 +++++++++++++++++++++++++++---------- hw/9pfs/9p-local.h | 20 ++++++++++++++++++++ 2 files changed, 47 insertions(+), 10 deletions(-) create mode 100644 hw/9pfs/9p-local.h diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index be6be615149b..2c491af623f9 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -13,6 +13,7 @@ #include "qemu/osdep.h" #include "9p.h" +#include "9p-local.h" #include "9p-xattr.h" #include "9p-util.h" #include "fsdev/qemu-fsdev.h" /* local_ops */ @@ -48,6 +49,24 @@ typedef struct { int mountfd; } LocalData; +int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags, + mode_t mode) +{ + LocalData *data = fs_ctx->private; + + /* All paths are relative to the path data->mountfd points to */ + while (*path == '/') { + path++; + } + + return relative_openat_nofollow(data->mountfd, path, flags, mode); +} + +int local_opendir_nofollow(FsContext *fs_ctx, const char *path) +{ + return local_open_nofollow(fs_ctx, path, O_DIRECTORY | O_RDONLY, 0); +} + #define VIRTFS_META_DIR ".virtfs_metadata" static char *local_mapped_attr_path(FsContext *ctx, const char *path) @@ -359,13 +378,9 @@ static int local_closedir(FsContext *ctx, V9fsFidOpenState *fs) static int local_open(FsContext *ctx, V9fsPath *fs_path, int flags, V9fsFidOpenState *fs) { - char *buffer; - char *path = fs_path->data; int fd; - buffer = rpath(ctx, path); - fd = open(buffer, flags | O_NOFOLLOW); - g_free(buffer); + fd = local_open_nofollow(ctx, fs_path->data, flags, 0); if (fd == -1) { return -1; } @@ -376,13 +391,15 @@ static int local_open(FsContext *ctx, V9fsPath *fs_path, static int local_opendir(FsContext *ctx, V9fsPath *fs_path, V9fsFidOpenState *fs) { - char *buffer; - char *path = fs_path->data; + int dirfd; DIR *stream; - buffer = rpath(ctx, path); - stream = opendir(buffer); - g_free(buffer); + dirfd = local_opendir_nofollow(ctx, fs_path->data); + if (dirfd == -1) { + return -1; + } + + stream = fdopendir(dirfd); if (!stream) { return -1; } diff --git a/hw/9pfs/9p-local.h b/hw/9pfs/9p-local.h new file mode 100644 index 000000000000..32c72749d9df --- /dev/null +++ b/hw/9pfs/9p-local.h @@ -0,0 +1,20 @@ +/* + * 9p local backend utilities + * + * Copyright IBM, Corp. 2017 + * + * Authors: + * Greg Kurz + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#ifndef QEMU_9P_LOCAL_H +#define QEMU_9P_LOCAL_H + +int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags, + mode_t mode); +int local_opendir_nofollow(FsContext *fs_ctx, const char *path); + +#endif -- 2.7.4