From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vegard Nossum Subject: [PATCH] netlink: fix (theoretical) overrun in message iteration Date: Sun, 21 Dec 2008 14:42:18 +0100 Message-ID: <20081221134218.GA7959@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Thomas Graf , Eugene Teo , Andrew Morton , Al Viro , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: "David S. Miller" Return-path: Received: from ik-out-1112.google.com ([66.249.90.176]:25894 "EHLO ik-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751882AbYLUNkl (ORCPT ); Sun, 21 Dec 2008 08:40:41 -0500 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: >>From bb805d89e84ddb11c9bb58afcfd9a6b37bbe5a9b Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Sun, 21 Dec 2008 14:20:49 +0100 Subject: [PATCH] netlink: fix (theoretical) overrun in message iteration See commit 1045b03e07d85f3545118510a587035536030c1c for a detailed explanation of why this patch is necessary. In short, nlmsg_next() can make "remaining" go negative, and the remaining >= sizeof(...) comparison will promote "remaining" to an unsigned type, which means that the expression will evaluate to true for negative numbers, even though it was not intended. I put "theoretical" in the title because I have no evidence that this can actually happen, but I suspect that a crafted netlink packet can trigger some badness. Note that the last test, which seemingly has the exact same problem (also true for nla_ok()), is perfectly OK, since we already know that remaining is positive. Cc: Thomas Graf Signed-off-by: Vegard Nossum --- include/net/netlink.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/include/net/netlink.h b/include/net/netlink.h index 3643bbb..13dd525 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -332,7 +332,7 @@ static inline int nlmsg_attrlen(const struct nlmsghdr *nlh, int hdrlen) */ static inline int nlmsg_ok(const struct nlmsghdr *nlh, int remaining) { - return (remaining >= sizeof(struct nlmsghdr) && + return (remaining >= (int) sizeof(struct nlmsghdr) && nlh->nlmsg_len >= sizeof(struct nlmsghdr) && nlh->nlmsg_len <= remaining); } -- 1.5.6.5