linux-kernel - [PATCH 4.4 29/50] net: core: Prevent from dereferencing null pointer when releasing SKB

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Message-Id: <20171006083709.838612955@linuxfoundation.org>
Date:   Fri,  6 Oct 2017 10:53:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Myungho Jung <mhjungk@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.4 29/50] net: core: Prevent from dereferencing null pointer when releasing SKB

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Myungho Jung <mhjungk@...il.com>


[ 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@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/dev.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2338,6 +2338,9 @@ void __dev_kfree_skb_irq(struct sk_buff
 {
 	unsigned long flags;
 
+	if (unlikely(!skb))
+		return;
+
 	if (likely(atomic_read(&skb->users) == 1)) {
 		smp_rmb();
 		atomic_set(&skb->users, 0);