From b9ff317b5cd4a8f7ca13934af679e129c3f1d2ce Mon Sep 17 00:00:00 2001
From: Myungho Jung <mhjungk@gmail.com>
Date: Tue, 25 Apr 2017 11:58:15 -0700
Subject: [PATCH] net: core: Prevent from dereferencing null pointer when
 releasing SKB

[ Upstream commit 9899886d5e8ec5b343b1efe44f185a0e68dc6454 ]

Added NULL check to make __dev_kfree_skb_irq consistent with kfree
family of functions.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=195289

Signed-off-by: Myungho Jung <mhjungk@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/core/dev.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 24d243084aab..dac52fa60f25 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2338,6 +2338,9 @@ void __dev_kfree_skb_irq(struct sk_buff *skb, enum skb_free_reason reason)
 {
 	unsigned long flags;
 
+	if (unlikely(!skb))
+		return;
+
 	if (likely(atomic_read(&skb->users) == 1)) {
 		smp_rmb();
 		atomic_set(&skb->users, 0);