From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754031AbaD1Baz (ORCPT ); Sun, 27 Apr 2014 21:30:55 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43111 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752925AbaD1B3Y (ORCPT ); Sun, 27 Apr 2014 21:29:24 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Thomas Graf" , "Pablo Neira" , "Florian Westphal" , "David S. Miller" Date: Mon, 28 Apr 2014 02:11:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 12/94] netlink: don't compare the nul-termination in nla_strcmp In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.58-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Pablo Neira [ Upstream commit 8b7b932434f5eee495b91a2804f5b64ebb2bc835 ] nla_strcmp compares the string length plus one, so it's implicitly including the nul-termination in the comparison. int nla_strcmp(const struct nlattr *nla, const char *str) { int len = strlen(str) + 1; ... d = memcmp(nla_data(nla), str, len); However, if NLA_STRING is used, userspace can send us a string without the nul-termination. This is a problem since the string comparison will not match as the last byte may be not the nul-termination. Fix this by skipping the comparison of the nul-termination if the attribute data is nul-terminated. Suggested by Thomas Graf. Cc: Florian Westphal Cc: Thomas Graf Signed-off-by: Pablo Neira Ayuso Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- lib/nlattr.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/lib/nlattr.c +++ b/lib/nlattr.c @@ -299,9 +299,15 @@ int nla_memcmp(const struct nlattr *nla, */ int nla_strcmp(const struct nlattr *nla, const char *str) { - int len = strlen(str) + 1; - int d = nla_len(nla) - len; + int len = strlen(str); + char *buf = nla_data(nla); + int attrlen = nla_len(nla); + int d; + if (attrlen > 0 && buf[attrlen - 1] == '\0') + attrlen--; + + d = attrlen - len; if (d == 0) d = memcmp(nla_data(nla), str, len);