[3.11.y.z extended stable] Patch "net: sctp: check proc_dointvec result in proc_sctp_do_auth" has been added to staging queue

[Luis Henriques]

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

    net: sctp: check proc_dointvec result in proc_sctp_do_auth

to the linux-3.11.y-queue branch of the 3.11.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-3.11.y-queue

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

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 3c7a1e4820f43fdd3b66f80b3a93017a7dcde829 Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman at redhat.com>
Date: Wed, 18 Jun 2014 23:46:31 +0200
Subject: net: sctp: check proc_dointvec result in proc_sctp_do_auth

commit 24599e61b7552673dd85971cf5a35369cd8c119e upstream.

When writing to the sysctl field net.sctp.auth_enable, it can well
be that the user buffer we handed over to proc_dointvec() via
proc_sctp_do_auth() handler contains something other than integers.

In that case, we would set an uninitialized 4-byte value from the
stack to net->sctp.auth_enable that can be leaked back when reading
the sysctl variable, and it can unintentionally turn auth_enable
on/off based on the stack content since auth_enable is interpreted
as a boolean.

Fix it up by making sure proc_dointvec() returned sucessfully.

Fixes: b14878ccb7fa ("net: sctp: cache auth_enable per endpoint")
Reported-by: Florian Westphal <fwestpha at redhat.com>
Signed-off-by: Daniel Borkmann <dborkman at redhat.com>
Acked-by: Neil Horman <nhorman at tuxdriver.com>
Acked-by: Vlad Yasevich <vyasevich at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/sctp/sysctl.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index e41a43470b84..1fce794c9274 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -368,8 +368,7 @@ static int proc_sctp_do_auth(struct ctl_table *ctl, int write,
 		tbl.data = &net->sctp.auth_enable;

 	ret = proc_dointvec(&tbl, write, buffer, lenp, ppos);
-
-	if (write) {
+	if (write && ret == 0) {
 		struct sock *sk = net->sctp.ctl_sock;

 		net->sctp.auth_enable = new_value;
--
1.9.1