From: Sasha Levin <sasha.levin@oracle.com>
Date: Thu, 7 Jan 2016 19:52:43 +0000 (-0500)
Subject: net: sctp: prevent writes to cookie_hmac_alg from accessing invalid memory
X-Git-Tag: v3.16.35~682
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3c2a56196667a2469f8c88dccce0487fa5ed0437;p=thirdparty%2Fkernel%2Fstable.git

net: sctp: prevent writes to cookie_hmac_alg from accessing invalid memory

commit 320f1a4a175e7cd5d3f006f92b4d4d3e2cbb7bb5 upstream.

proc_dostring() needs an initialized destination string, while the one
provided in proc_sctp_do_hmac_alg() contains stack garbage.

Thus, writing to cookie_hmac_alg would strlen() that garbage and end up
accessing invalid memory.

Fixes: 3c68198e7 ("sctp: Make hmac algorithm selection for cookie generation dynamic")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 12c7e01c26771..0b8583647355a 100644
--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -324,7 +324,7 @@ static int proc_sctp_do_hmac_alg(struct ctl_table *ctl, int write,
 	struct ctl_table tbl;
 	bool changed = false;
 	char *none = "none";
-	char tmp[8];
+	char tmp[8] = {0};
 	int ret;
 
 	memset(&tbl, 0, sizeof(struct ctl_table));