[3.16.y-ckt stable] Patch "net: sctp: fix memory leak in auth key management" 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: fix memory leak in auth key management

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt2.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 0f46f1b6e058ba603f658a4881d8f7b0cbc2dc5f Mon Sep 17 00:00:00 2001
From: Daniel Borkmann <dborkman at redhat.com>
Date: Mon, 10 Nov 2014 18:00:09 +0100
Subject: net: sctp: fix memory leak in auth key management

commit 4184b2a79a7612a9272ce20d639934584a1f3786 upstream.

A very minimal and simple user space application allocating an SCTP
socket, setting SCTP_AUTH_KEY setsockopt(2) on it and then closing
the socket again will leak the memory containing the authentication
key from user space:

unreferenced object 0xffff8800837047c0 (size 16):
  comm "a.out", pid 2789, jiffies 4296954322 (age 192.258s)
  hex dump (first 16 bytes):
    01 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff816d7e8e>] kmemleak_alloc+0x4e/0xb0
    [<ffffffff811c88d8>] __kmalloc+0xe8/0x270
    [<ffffffffa0870c23>] sctp_auth_create_key+0x23/0x50 [sctp]
    [<ffffffffa08718b1>] sctp_auth_set_key+0xa1/0x140 [sctp]
    [<ffffffffa086b383>] sctp_setsockopt+0xd03/0x1180 [sctp]
    [<ffffffff815bfd94>] sock_common_setsockopt+0x14/0x20
    [<ffffffff815beb61>] SyS_setsockopt+0x71/0xd0
    [<ffffffff816e58a9>] system_call_fastpath+0x12/0x17
    [<ffffffffffffffff>] 0xffffffffffffffff

This is bad because of two things, we can bring down a machine from
user space when auth_enable=1, but also we would leave security sensitive
keying material in memory without clearing it after use. The issue is
that sctp_auth_create_key() already sets the refcount to 1, but after
allocation sctp_auth_set_key() does an additional refcount on it, and
thus leaving it around when we free the socket.

Fixes: 65b07e5d0d0 ("[SCTP]: API updates to suport SCTP-AUTH extensions.")
Signed-off-by: Daniel Borkmann <dborkman at redhat.com>
Cc: Vlad Yasevich <vyasevich at gmail.com>
Acked-by: Neil Horman <nhorman at tuxdriver.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/sctp/auth.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 0e8529113dc5..fb7976aee61c 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -862,8 +862,6 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
 		list_add(&cur_key->key_list, sh_keys);

 	cur_key->key = key;
-	sctp_auth_key_hold(key);
-
 	return 0;
 nomem:
 	if (!replace)
--
2.1.0