[PATCH review for 3.18 18/30] net: core: Prevent from dereferencing null pointer when releasing SKB

From: Levin, Alexander (Sasha Levin)
Date: Wed Sep 20 2017 - 00:47:19 EST


From: Myungho Jung <mhjungk@xxxxxxxxx>

[ 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@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
net/core/dev.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 22ad4e433b3a..21b0bd976699 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2225,6 +2225,9 @@ 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);
--
2.11.0