From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37168) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bw9Uo-0000le-41 for qemu-devel@nongnu.org; Mon, 17 Oct 2016 11:06:36 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bw9Ui-0005Lg-MD for qemu-devel@nongnu.org; Mon, 17 Oct 2016 11:06:34 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56295) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1bw9Ui-0005LO-CZ for qemu-devel@nongnu.org; Mon, 17 Oct 2016 11:06:28 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id u9HF54hH118695 for ; Mon, 17 Oct 2016 11:06:27 -0400 Received: from e06smtp14.uk.ibm.com (e06smtp14.uk.ibm.com [195.75.94.110]) by mx0a-001b2d01.pphosted.com with ESMTP id 264wef42f4-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 17 Oct 2016 11:06:27 -0400 Received: from localhost by e06smtp14.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 17 Oct 2016 16:06:24 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id E80962190056 for ; Mon, 17 Oct 2016 16:05:37 +0100 (BST) Received: from d06av11.portsmouth.uk.ibm.com (d06av11.portsmouth.uk.ibm.com [9.149.37.252]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u9HF6LFg22937656 for ; Mon, 17 Oct 2016 15:06:21 GMT Received: from d06av11.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av11.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u9HF6Kd1006752 for ; Mon, 17 Oct 2016 09:06:20 -0600 From: Greg Kurz Date: Mon, 17 Oct 2016 17:05:43 +0200 In-Reply-To: <1476716754-26686-1-git-send-email-groug@kaod.org> References: <1476716754-26686-1-git-send-email-groug@kaod.org> Message-Id: <1476716754-26686-2-git-send-email-groug@kaod.org> Subject: [Qemu-devel] [PULL 01/12] 9pfs: allocate space for guest originated empty strings 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 , Li Qiang From: Li Qiang If a guest sends an empty string paramater to any 9P operation, the current code unmarshals it into a V9fsString equal to { .size = 0, .data = NULL }. This is unfortunate because it can cause NULL pointer dereference to happen at various locations in the 9pfs code. And we don't want to check str->data everywhere we pass it to strcmp() or any other function which expects a dereferenceable pointer. This patch enforces the allocation of genuine C empty strings instead, so callers don't have to bother. Out of all v9fs_iov_vunmarshal() users, only v9fs_xattrwalk() checks if the returned string is empty. It now uses v9fs_string_size() since name.data cannot be NULL anymore. Signed-off-by: Li Qiang [groug, rewritten title and changelog, fix empty string check in v9fs_xattrwalk()] Signed-off-by: Greg Kurz --- fsdev/9p-iov-marshal.c | 2 +- hw/9pfs/9p.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fsdev/9p-iov-marshal.c b/fsdev/9p-iov-marshal.c index 663cad542900..1d16f8df4bd4 100644 --- a/fsdev/9p-iov-marshal.c +++ b/fsdev/9p-iov-marshal.c @@ -125,7 +125,7 @@ ssize_t v9fs_iov_vunmarshal(struct iovec *out_sg, int out_num, size_t offset, str->data = g_malloc(str->size + 1); copied = v9fs_unpack(str->data, out_sg, out_num, offset, str->size); - if (copied > 0) { + if (copied >= 0) { str->data[str->size] = 0; } else { v9fs_string_free(str); diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c index 119ee584969b..39a7e1d52d2a 100644 --- a/hw/9pfs/9p.c +++ b/hw/9pfs/9p.c @@ -3174,7 +3174,7 @@ static void v9fs_xattrwalk(void *opaque) goto out; } v9fs_path_copy(&xattr_fidp->path, &file_fidp->path); - if (name.data == NULL) { + if (!v9fs_string_size(&name)) { /* * listxattr request. Get the size first */ -- 2.5.5