linux-kernel - [PATCH 3.16.y-ckt 008/180] net: sctp: prevent writes to cookie_hmac

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Message-Id: <1454538786-12215-9-git-send-email-luis.henriques@canonical.com>
Date:	Wed,  3 Feb 2016 22:30:14 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	"David S . Miller" <davem@...emloft.net>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 008/180] net: sctp: prevent writes to cookie_hmac_alg from accessing invalid memory

3.16.7-ckt24 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Sasha Levin <sasha.levin@...cle.com>

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@...cle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 net/sctp/sysctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/sysctl.c b/net/sctp/sysctl.c
index 12c7e01c2677..0b8583647355 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));