From: Ido Schimmel <idosch@nvidia.com>
To: Chenguang Zhao <chenguang.zhao@linux.dev>
Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com, horms@kernel.org, dsahern@kernel.org,
kerneljasonxing@gmail.com, netdev@vger.kernel.org,
Chenguang Zhao <zhaochenguang@kylinos.cn>,
syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com, ja@ssi.bg
Subject: Re: [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear
Date: Fri, 25 Sep 2026 15:42:42 +0300 [thread overview]
Message-ID: <20260925124242.GA112355@shredder> (raw)
In-Reply-To: <20260924063312.1194019-1-chenguang.zhao@linux.dev>
On Thu, Sep 24, 2026 at 02:33:12PM +0800, Chenguang Zhao wrote:
> From: Chenguang Zhao <zhaochenguang@kylinos.cn>
>
> Commit de2c211868b9 ("ipvs: Always clear ipvs_property flag in
> skb_scrub_packet()") moved ipvs_reset() before the xnet check, making
> the call unconditional. The intent was to fix a bpf_redirect case where
> stale ipvs_property on an skb re-entering the RX path caused the SNAT
> hook to be skipped. However the change is too broad: when IPVS NAT
> sits above an ipvlan L3 interface in the same netns, the following
> loop happens:
>
> LOCAL_OUT -> IPVS DNAT (sets ipvs_property=1) -> dst_output -> ipvlan
> -> skb_scrub_packet() -> ipvs_reset() clears the flag
> -> ipvlan_process_v4_outbound() -> ip_local_out() -> LOCAL_OUT
> -> IPVS sees ipvs_property=0, processes again -> infinite recursion
>
> syzbot reported this as a stack overflow on a KASAN kernel where each
> level burns ~3.3 KB of stack and XMIT_RECURSION_LIMIT falls short. On
> non-KASAN kernels the dead-loop detector catches it and prints "Dead
> loop on virtual device", but traffic is still broken.
>
> Fixes: de2c211868b9 ("ipvs: Always clear ipvs_property flag in skb_scrub_packet()")
> Reported-by: syzbot+2b120190d9e54ad8c65d@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=2b120190d9e54ad8c65d
> Signed-off-by: Chenguang Zhao <zhaochenguang@kylinos.cn>
1. You need to copy IPVS maintainers on patches related to IPVS. Added
Julian.
2. Does it reproduce with commit 7f1de03e3103 ("net: reduce
XMIT_RECURSION_LIMIT under KASAN") in net-next?
next prev parent reply other threads:[~2026-09-25 12:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-24 6:33 [PATCH net] ipvs: fix infinite loop with ipvlan L3 from unconditional ipvs_property clear Chenguang Zhao
2026-09-25 12:42 ` Ido Schimmel [this message]
2026-09-28 6:55 ` Chenguang Zhao
2026-09-28 8:10 ` Julian Anastasov
2026-09-26 20:12 ` [syzbot ci] " syzbot ci
2026-09-28 6:58 ` [PATCH net] " netdev-bot+sashiko
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