From: Simon Horman <horms@kernel.org>
To: "Jérémy Jean" <Jeremy.Jean@oss.cyber.gouv.fr>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: gue: reject invalid REMCSUM offsets
Date: Mon, 24 Aug 2026 13:27:06 +0100 [thread overview]
Message-ID: <20260824122706.GR265046@horms.kernel.org> (raw)
In-Reply-To: <20260820220210.3122690-2-Jeremy.Jean@oss.cyber.gouv.fr>
On Thu, Aug 20, 2026 at 10:02:10PM +0000, Jérémy Jean wrote:
> The REMCSUM option carries an absolute checksum start and checksum field
> offset. gue_remcsum() passes them to skb_remcsum_process(), whose
> partial path stores offset - start in the u16 skb->csum_offset. If
> offset is less than start, this underflows (for example, 1/0 becomes
> 0xffff).
>
> A forwarded packet can retain CHECKSUM_PARTIAL and reach a
> NETIF_F_HW_CSUM driver which trusts the metadata, leading
> skb_copy_and_csum_dev() to write two bytes about 64 KiB beyond the
> destination buffer.
>
> Reject reversed tuples in both normal and GRO receive paths.
>
> Fixes: fe881ef11cf0 ("gue: Use checksum partial with remote checksum offload")
> Assisted-by: Codex:gpt-5
> Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2026-08-24 12:27 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-20 22:02 Jérémy Jean
2026-08-24 12:27 ` Simon Horman [this message]
2026-08-24 13:38 ` Eric Dumazet
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