From 0e24c4fc52b16f0a1102a933f636d2f350c41098 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Thu, 11 Oct 2012 06:24:14 +0000
Subject: tcp: sysctl interface leaks 16 bytes of kernel memory

If the rc_dereference of tcp_fastopen_ctx ever fails then we copy 16 bytes
of kernel stack into the proc result.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 9205e49..63d4ecc 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -248,6 +248,8 @@ int proc_tcp_fastopen_key(ctl_table *ctl, int write, void __user *buffer,
 	ctxt = rcu_dereference(tcp_fastopen_ctx);
 	if (ctxt)
 		memcpy(user_key, ctxt->key, TCP_FASTOPEN_KEY_LENGTH);
+	else
+		memset(user_key, 0, sizeof(user_key));
 	rcu_read_unlock();
 
 	snprintf(tbl.data, tbl.maxlen, "%08x-%08x-%08x-%08x",
-- 
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