5.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit 8156210d36a43e76372312c87eb5ea3dbb405a85 ]
Bernard Pidoux reported a regression apparently caused by commit c353e8983e0d ("net: introduce per netns packet 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 a major crash.
But the root cause is that ax25_kiss_rcv() can queue/mangle input skb without checking if this skb is shared or not.
Many thanks to Bernard Pidoux for his help, diagnosis and tests.
We had a similar issue years ago fixed with commit 7aaed57c5c28 ("phonet: properly unshare skbs in phonet_rcv()").
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Bernard Pidoux f6bvp@free.fr Closes: https://lore.kernel.org/netdev/1713f383-c538-4918-bc64-13b3288cd542@free.fr/ Tested-by: Bernard Pidoux f6bvp@free.fr Signed-off-by: Eric Dumazet edumazet@google.com Cc: Joerg Reuter jreuter@yaina.de Cc: David Ranch dranch@trinnet.net Cc: Folkert van Heusden folkert@vanheusden.com Reviewed-by: Dan Cross crossd@gmail.com Link: https://patch.msgid.link/20250902124642.212705-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ax25/ax25_in.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/net/ax25/ax25_in.c b/net/ax25/ax25_in.c index dcdbaeeb2358a..506a88b2357bf 100644 --- a/net/ax25/ax25_in.c +++ b/net/ax25/ax25_in.c @@ -433,6 +433,10 @@ static int ax25_rcv(struct sk_buff *skb, struct net_device *dev, int ax25_kiss_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *ptype, struct net_device *orig_dev) { + skb = skb_share_check(skb, GFP_ATOMIC); + if (!skb) + return NET_RX_DROP; + skb_orphan(skb);
if (!net_eq(dev_net(dev), &init_net)) {