linux-kernel - [PATCH 4.4 38/67] net: sctp: prevent writes to cookie_hmac

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Message-Id: <20160127180911.926571820@linuxfoundation.org>
Date:	Wed, 27 Jan 2016 10:12:32 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Sasha Levin <sasha.levin@...cle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 38/67] net: sctp: prevent writes to cookie_hmac_alg from accessing invalid memory

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

------------------

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

[ Upstream commit 320f1a4a175e7cd5d3f006f92b4d4d3e2cbb7bb5 ]

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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/sctp/sysctl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sctp/sysctl.c
+++ b/net/sctp/sysctl.c
@@ -320,7 +320,7 @@ static int proc_sctp_do_hmac_alg(struct
 	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));