From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: Eric Dumazet <edumazet@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>
Cc: Willem de Bruijn <willemb@google.com>,
Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Eric Dumazet <edumazet@kernel.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
Aaron Conole <aconole@redhat.com>,
Eelco Chaudron <echaudro@redhat.com>,
Ilya Maximets <i.maximets@ovn.org>,
Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
dev@openvswitch.org,
Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
Ren Wei <weir@nebusec.ai>, Vega <vega@nebusec.ai>
Subject: Re: [PATCH net v2 2/5] loopback: use eth_type_trans_careful()
Date: Wed, 28 Oct 2026 14:48:32 -0400 [thread overview]
Message-ID: <willemdebruijn.kernel.1010e42464cde@gmail.com> (raw)
In-Reply-To: <20261028122703.2093730-3-edumazet@kernel.org>
Eric Dumazet wrote:
> tc egress actions can leave an skb with fewer than ETH_HLEN bytes in
> its linear part. loopback_xmit() then crashes in eth_type_trans():
>
> tc qdisc add dev lo clsact
> tc filter add dev lo egress matchall action vlan pop_eth
> # AF_PACKET SOCK_RAW: eth / eth / 8192 bytes of payload
>
> kernel BUG at include/linux/skbuff.h:2839!
> RIP: 0010:eth_type_trans (include/linux/etherdevice.h:635 net/ethernet/eth.c:163)
> Call Trace:
> loopback_xmit (drivers/net/loopback.c:87)
> dev_hard_start_xmit (include/linux/netdevice.h:5455 include/linux/netdevice.h:5464 net/core/dev.c:4057 net/core/dev.c:4073)
> __dev_queue_xmit (net/core/dev.c:5066)
> packet_sendmsg (net/packet/af_packet.c:3157 net/packet/af_packet.c:3189)
>
> The same happens with "action ife decode" on lo egress.
>
> Use eth_type_trans_careful(), and drop the packet if the Ethernet
> header can not be pulled.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Reported-by: Vega <vega@nebusec.ai>
> Link: https://lore.kernel.org/netdev/20261005052249.1914367-2-weir@nebusec.ai/
> Signed-off-by: Eric Dumazet <edumazet@kernel.org>
> Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com>
> Tested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
next prev parent reply other threads:[~2026-10-28 18:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-28 12:26 [PATCH net v2 0/5] net: fix eth_type_trans() crashes on skbs coming from the stack Eric Dumazet
2026-10-28 12:26 ` [PATCH net v2 1/5] net: add eth_type_trans_careful() Eric Dumazet
2026-10-28 12:27 ` [PATCH net v2 2/5] loopback: use eth_type_trans_careful() Eric Dumazet
2026-10-28 18:48 ` Willem de Bruijn [this message]
2026-10-28 12:27 ` [PATCH net v2 3/5] net: use eth_type_trans_careful() in __dev_forward_skb2() Eric Dumazet
2026-10-28 19:03 ` Willem de Bruijn
2026-10-28 12:27 ` [PATCH net v2 4/5] openvswitch: use eth_type_trans_careful() in internal_dev_recv() Eric Dumazet
2026-10-28 19:04 ` Willem de Bruijn
2026-10-28 12:27 ` [PATCH net v2 5/5] net/sched: act_ife: do not consume the inner header on egress Eric Dumazet
2026-10-28 17:34 ` [PATCH net v2 0/5] net: fix eth_type_trans() crashes on skbs coming from the stack Alexei Starovoitov
2026-10-28 19:31 ` Daniel Borkmann
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