From: Jakub Kicinski <kuba@kernel.org>
To: Yun Lu <luyun_611@163.com>
Cc: davem@davemloft.net, edumazet@google.com, pabeni@redhat.com,
horms@kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bpf: lwtunnel: Check skb->_skb_refdst in bpf_lwt_push_ip_encap
Date: Tue, 27 Jan 2026 16:00:52 -0800 [thread overview]
Message-ID: <20260127160052.5038cc7b@kernel.org> (raw)
In-Reply-To: <20260127084520.13890-1-luyun_611@163.com>
On Tue, 27 Jan 2026 16:45:20 +0800 Yun Lu wrote:
> The bpf_lwt_xmit_push_encap helper needs to access skb_dst(skb)->dev to
> calculate the needed headroom:
>
> err = skb_cow_head(skb,
> len + LL_RESERVED_SPACE(skb_dst(skb)->dev));
>
> But skb->_skb_refdst may not be initialized when the skb is set up by
> bpf_prog_test_run_skb function. Executing bpf_lwt_push_ip_encap function
> in this scenario will trigger null pointer dereference, causing a kernel
> crash as Yinhao reported:
Seems a bit backwards to be adding datapath checks to make
bpf_prog_test_run_skb() happy. Also - please run checkpatch.
--
pw-bot: cr
prev parent reply other threads:[~2026-01-28 0:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-27 8:45 [PATCH] bpf: lwtunnel: Check skb->_skb_refdst in bpf_lwt_push_ip_encap Yun Lu
2026-01-28 0:00 ` Jakub Kicinski [this message]
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