From: Eric Dumazet Date: Tue, 2 Sep 2025 12:46:42 +0000 (+0000) Subject: ax25: properly unshare skbs in ax25_kiss_rcv() X-Git-Tag: v6.17-rc5~21^2~8 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8156210d36a43e76372312c87eb5ea3dbb405a85;p=thirdparty%2Fkernel%2Fstable.git ax25: properly unshare skbs in ax25_kiss_rcv() 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 Closes: https://lore.kernel.org/netdev/1713f383-c538-4918-bc64-13b3288cd542@free.fr/ Tested-by: Bernard Pidoux Signed-off-by: Eric Dumazet Cc: Joerg Reuter Cc: David Ranch Cc: Folkert van Heusden Reviewed-by: Dan Cross Link: https://patch.msgid.link/20250902124642.212705-1-edumazet@google.com Signed-off-by: Jakub Kicinski --- diff --git a/net/ax25/ax25_in.c b/net/ax25/ax25_in.c index 1cac25aca6378..f2d66af863595 100644 --- a/net/ax25/ax25_in.c +++ b/net/ax25/ax25_in.c @@ -433,6 +433,10 @@ free: 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)) {