linux-kernel - [PATCH 3.11 037/137] net: sctp: check proc_dointvec result in proc_sctp_do

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Message-Id: <1408354398-10226-38-git-send-email-luis.henriques@canonical.com>
Date:	Mon, 18 Aug 2014 10:31:38 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Daniel Borkmann <dborkman@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.11 037/137] net: sctp: check proc_dointvec result in proc_sctp_do_auth

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

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

From: Daniel Borkmann <dborkman@...hat.com>

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@...hat.com>
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
Acked-by: Neil Horman <nhorman@...driver.com>
Acked-by: Vlad Yasevich <vyasevich@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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

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