[3.8.y.z extended stable] Patch "netlink: don't compare the nul-termination in nla_strcmp" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    netlink: don't compare the nul-termination in nla_strcmp

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.22.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6a626eacfdf771d245366fce5173f42545940e33 Mon Sep 17 00:00:00 2001
From: Pablo Neira <pablo at netfilter.org>
Date: Tue, 1 Apr 2014 19:38:44 +0200
Subject: netlink: don't compare the nul-termination in nla_strcmp

[ 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 <fw at strlen.de>
Cc: Thomas Graf <tgraf at suug.ch>
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 lib/nlattr.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 18eca78..fc67547 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -303,9 +303,15 @@ int nla_memcmp(const struct nlattr *nla, const void *data,
  */
 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);

--
1.8.3.2