Patch "driver: vrf: Fix one possible use-after-free issue" has been added to the 4.9-stable tree

Patch "driver: vrf: Fix one possible use-after-free issue" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    driver: vrf: Fix one possible use-after-free issue

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     driver-vrf-fix-one-possible-use-after-free-issue.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed May 31 09:13:34 JST 2017
From: Gao Feng <gfree.wind@vip.163.com>
Date: Tue, 9 May 2017 18:27:33 +0800
Subject: driver: vrf: Fix one possible use-after-free issue

From: Gao Feng <gfree.wind@vip.163.com>


[ Upstream commit 1a4a5bf52a4adb477adb075e5afce925824ad132 ]

The current codes only deal with the case that the skb is dropped, it
may meet one use-after-free issue when NF_HOOK returns 0 that means
the skb is stolen by one netfilter rule or hook.

When one netfilter rule or hook stoles the skb and return NF_STOLEN,
it means the skb is taken by the rule, and other modules should not
touch this skb ever. Maybe the skb is queued or freed directly by the
rule.

Now uses the nf_hook instead of NF_HOOK to get the result of netfilter,
and check the return value of nf_hook. Only when its value equals 1, it
means the skb could go ahead. Or reset the skb as NULL.

BTW, because vrf_rcv_finish is empty function, so needn't invoke it
even though nf_hook returns 1. But we need to modify vrf_rcv_finish
to deal with the NF_STOLEN case.

There are two cases when skb is stolen.
1. The skb is stolen and freed directly.
   There is nothing we need to do, and vrf_rcv_finish isn't invoked.
2. The skb is queued and reinjected again.
   The vrf_rcv_finish would be invoked as okfn, so need to free the
   skb in it.

Signed-off-by: Gao Feng <gfree.wind@vip.163.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/vrf.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/vrf.c
+++ b/drivers/net/vrf.c
@@ -850,6 +850,7 @@ static u32 vrf_fib_table(const struct ne
 
 static int vrf_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
+	kfree_skb(skb);
 	return 0;
 }
 
@@ -859,7 +860,7 @@ static struct sk_buff *vrf_rcv_nfhook(u8
 {
 	struct net *net = dev_net(dev);
 
-	if (NF_HOOK(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) < 0)
+	if (nf_hook(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) != 1)
 		skb = NULL;    /* kfree_skb(skb) handled by nf code */
 
 	return skb;


Patches currently in stable-queue which might be from gfree.wind@vip.163.com are

queue-4.9/driver-vrf-fix-one-possible-use-after-free-issue.patch