netdev - [PATCH] tcp: sysctl interface leaks 16 bytes of kernel memory

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Message-ID: <20121011162407.2590.40301.stgit@bob.linux.org.uk>
Date:	Thu, 11 Oct 2012 17:24:14 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	netdev@...r.kernel.org
Subject: [PATCH] tcp: sysctl interface leaks 16 bytes of kernel memory

From: Alan Cox <alan@...ux.intel.com>

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@...ux.intel.com>
---

 net/ipv4/sysctl_net_ipv4.c |    2 ++
 1 file changed, 2 insertions(+)


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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