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Subject[PATCH net] phonet: properly unshare skbs in phonet_rcv()
From
Date
From: Eric Dumazet <edumazet@google.com>

Ivaylo Dimitrov reported a regression caused by commit 7866a621043f
("dev: add per net_device packet type chains").

skb->dev becomes NULL and we crash in __netif_receive_skb_core().

Before above commit, different kind of bugs or corruptions could happen
without major crash.

But the root cause is that phonet_rcv() can queue skb without checking
if skb is shared or not.

Many thanks to Ivaylo Dimitrov for his help, diagnosis and tests.

Reported-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Tested-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Remi Denis-Courmont <courmisch@gmail.com>
---
net/phonet/af_phonet.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/net/phonet/af_phonet.c b/net/phonet/af_phonet.c
index 10d42f3220ab..f925753668a7 100644
--- a/net/phonet/af_phonet.c
+++ b/net/phonet/af_phonet.c
@@ -377,6 +377,10 @@ static int phonet_rcv(struct sk_buff *skb, struct net_device *dev,
struct sockaddr_pn sa;
u16 len;

+ skb = skb_share_check(skb, GFP_ATOMIC);
+ if (!skb)
+ return NET_RX_DROP;
+
/* check we have at least a full Phonet header */
if (!pskb_pull(skb, sizeof(struct phonethdr)))
goto out;

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