Patchwork tcp: sysctl interface leaks 16 bytes of kernel memory

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Submitter Alan Cox
Date Oct. 11, 2012, 4:24 p.m.
Message ID <20121011162407.2590.40301.stgit@bob.linux.org.uk>
Download mbox | patch
Permalink /patch/190956/
State Accepted
Delegated to: David Miller
Headers show

Comments

Alan Cox - Oct. 11, 2012, 4:24 p.m.
From: Alan Cox <alan@linux.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@linux.intel.com>
---

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



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David Miller - Oct. 11, 2012, 7:13 p.m.
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
Date: Thu, 11 Oct 2012 17:24:14 +0100

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

Applied and queued up for -stable.
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Patch

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",