From: Antoine Tenart <atenart@kernel.org>
To: xuanqiang.luo@linux.dev
Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
tom@herbertland.com, aduyck@mirantis.com,
linux-kernel@vger.kernel.org,
Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Subject: Re: [PATCH net v1] udp: fix potential use-after-free in tunnel segmentation
Date: Thu, 30 Jul 2026 17:45:08 +0200 [thread overview]
Message-ID: <amtxfCFLD-nlsdTm@kwain> (raw)
In-Reply-To: <20260730093554.68127-1-xuanqiang.luo@linux.dev>
On Thu, Jul 30, 2026 at 05:35:54PM +0800, xuanqiang.luo@linux.dev wrote:
> From: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
>
> __skb_udp_tunnel_segment() gets the UDP header before ensuring the
> tunnel header is in the skb head. If the pull reallocates skb->head,
> the saved UDP header pointer is no longer valid.
>
> Get the UDP header after the pull to avoid a potential use-after-free.
>
> Fixes: dbef491ebe7f ("udp: Use uh->len instead of skb->len to compute checksum in segmentation")
> Signed-off-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
> ---
> net/ipv4/udp_offload.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 29651b1a0bc70..639c59044c135 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -178,7 +178,7 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
> int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
> bool remcsum, need_csum, offload_csum, gso_partial;
> struct sk_buff *segs = ERR_PTR(-EINVAL);
> - struct udphdr *uh = udp_hdr(skb);
> + struct udphdr *uh;
> u16 mac_offset = skb->mac_header;
> __be16 protocol = skb->protocol;
> u16 mac_len = skb->mac_len;
> @@ -189,6 +189,8 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
> if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
> goto out;
>
> + uh = udp_hdr(skb);
> +
> /* Adjust partial header checksum to negate old length.
> * We cannot rely on the value contained in uh->len as it is
> * possible that the actual value exceeds the boundaries of the
> --
> 2.43.0
>
prev parent reply other threads:[~2026-07-30 15:45 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-30 9:35 [PATCH net v1] udp: fix potential use-after-free in tunnel segmentation xuanqiang.luo
2026-07-30 15:45 ` Antoine Tenart [this message]
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