From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37652) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cif3k-0001Gz-LJ for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cif3h-0007ys-AG for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:08 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:33687) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cif3h-0007yI-0C for qemu-devel@nongnu.org; Tue, 28 Feb 2017 05:31:05 -0500 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v1SASlfS055073 for ; Tue, 28 Feb 2017 05:31:04 -0500 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 28vnaj7syk-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Tue, 28 Feb 2017 05:31:03 -0500 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 28 Feb 2017 10:31:01 -0000 From: Greg Kurz Date: Tue, 28 Feb 2017 11:30:24 +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: <1488277840-18608-13-git-send-email-groug@kaod.org> Subject: [Qemu-devel] [PULL 12/28] 9pfs: local: remove: 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_remove() callback is vulnerable to symlink attacks because it calls: (1) lstat() which follows symbolic links in all path elements but the rightmost one (2) remove() which follows symbolic links in all path elements but the rightmost one This patch converts local_remove() to rely on opendir_nofollow(), fstatat(AT_SYMLINK_NOFOLLOW) to fix (1) and unlinkat() to fix (2). This partly fixes CVE-2016-9602. Signed-off-by: Greg Kurz Reviewed-by: Stefan Hajnoczi --- hw/9pfs/9p-local.c | 64 ++++++++++++++++++------------------------------------ 1 file changed, 21 insertions(+), 43 deletions(-) diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c index 04de511765d8..8fb79e44b5f3 100644 --- a/hw/9pfs/9p-local.c +++ b/hw/9pfs/9p-local.c @@ -1021,54 +1021,32 @@ err_out: static int local_remove(FsContext *ctx, const char *path) { - int err; struct stat stbuf; - char *buffer; + char *dirpath = g_path_get_dirname(path); + char *name = g_path_get_basename(path); + int flags = 0; + int dirfd; + int err = -1; - if (ctx->export_flags & V9FS_SM_MAPPED_FILE) { - buffer = rpath(ctx, path); - err = lstat(buffer, &stbuf); - g_free(buffer); - if (err) { - goto err_out; - } - /* - * If directory remove .virtfs_metadata contained in the - * directory - */ - if (S_ISDIR(stbuf.st_mode)) { - buffer = g_strdup_printf("%s/%s/%s", ctx->fs_root, - path, VIRTFS_META_DIR); - err = remove(buffer); - g_free(buffer); - if (err < 0 && errno != ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file created - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } - } - /* - * Now remove the name from parent directory - * .virtfs_metadata directory - */ - buffer = local_mapped_attr_path(ctx, path); - err = remove(buffer); - g_free(buffer); - if (err < 0 && errno != ENOENT) { - /* - * We didn't had the .virtfs_metadata file. May be file created - * in non-mapped mode ?. Ignore ENOENT. - */ - goto err_out; - } + dirfd = local_opendir_nofollow(ctx, dirpath); + if (dirfd) { + goto out; } - buffer = rpath(ctx, path); - err = remove(buffer); - g_free(buffer); + if (fstatat(dirfd, path, &stbuf, AT_SYMLINK_NOFOLLOW) < 0) { + goto err_out; + } + + if (S_ISDIR(stbuf.st_mode)) { + flags |= AT_REMOVEDIR; + } + + err = local_unlinkat_common(ctx, dirfd, name, flags); err_out: + close_preserve_errno(dirfd); +out: + g_free(name); + g_free(dirpath); return err; } -- 2.7.4