From: Ido Schimmel <idosch@nvidia.com>
To: Zhiling Zou <zhilinz@nebusec.ai>
Cc: namangulati@google.com, netdev@vger.kernel.org,
dsahern@kernel.org, davem@davemloft.net, edumazet@kernel.org,
pabeni@redhat.com, horms@kernel.org, vega@nebusec.ai
Subject: Re: [PATCH net v3 1/1] ipmr: drop packets with unknown ingress VIF
Date: Thu, 22 Oct 2026 10:55:27 +0300 [thread overview]
Message-ID: <20261022075527.GA3591482@shredder> (raw)
In-Reply-To: <5271fcb94a4d9e697ed64a348e92ea9e74faab1c.1792608753.git.zhilinz@nebusec.ai>
On Thu, Oct 22, 2026 at 03:01:16AM +0800, Zhiling Zou wrote:
> A packet can race with VIF publication and make ipmr_find_vif() return
> -1 even though the VIF device pointer is already visible. The parent VIF
> device check can then pass with an invalid ingress VIF. For (*,G)
> entries, this can also let the packet be forwarded back out its ingress
> VIF.
>
> Drop packets whose ingress VIF lookup fails in both IPv4 and IPv6
> forwarding, before checking the MFC parent device. This prevents
> forwarding with an unknown ingress VIF and avoids the (*,G) hairpin.
>
> Without the early check, the negative index can reach the IPv4 offload
> lookup only for an skb marked for L3 forwarding offload, currently done
> by mlxsw. The race is rare; the supplied PoC reports only the UBSAN
> negative-index diagnostic.
>
> Fixes: 4eadb88244d1 ("ipmr: do not acquire mrt_lock while calling ip_mr_forward()")
> Fixes: 9b1c21d898fd ("ip6mr: do not acquire mrt_lock while calling ip6_mr_forward()")
> Cc: stable@vger.kernel.org
> Reported-by: Vega <vega@nebusec.ai>
> Link: https://lore.kernel.org/netdev/b966eb102e98f299e45be59ada033a8766e4c6df.1791899747.git.zhilinz@nebusec.ai/
> Suggested-by: Ido Schimmel <idosch@nvidia.com>
> Suggested-by: Naman Gulati <namangulati@google.com>
> Assisted-by: LLM
> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2026-10-22 7:55 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-21 19:01 [PATCH net v3 0/1] ipmr: drop packets with unknown ingress VIF Zhiling Zou
2026-10-21 19:01 ` [PATCH net v3 1/1] " Zhiling Zou
2026-10-21 19:34 ` Naman Gulati
2026-10-22 7:55 ` Ido Schimmel [this message]
2026-10-26 23:50 ` [PATCH net v3 0/1] " patchwork-bot+netdevbpf
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