netdev - Re: [PATCH net] net/mlx5: Correctly set gso

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANn89iJo5Fxx4kqhE4S+z4N0BtLW2462Pc6uBB2OvPDpo7-pKw@mail.gmail.com>
Date: Wed, 30 Jul 2025 05:28:46 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Gal Pressman <gal@...dia.com>, Willem de Bruijn <willemb@...gle.com>, Bailey Forrest <bcf@...gle.com>, 
	Catherine Sullivan <csully@...gle.com>
Cc: cpaasch@...nai.com, Saeed Mahameed <saeedm@...dia.com>, Tariq Toukan <tariqt@...dia.com>, 
	Mark Bloch <mbloch@...dia.com>, Leon Romanovsky <leon@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Amir Vadai <amirv@...lanox.com>, netdev@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net] net/mlx5: Correctly set gso_segs when LRO is used

On Wed, Jul 30, 2025 at 4:06 AM Gal Pressman <gal@...dia.com> wrote:
>
> On 29/07/2025 21:34, Christoph Paasch via B4 Relay wrote:
> > From: Christoph Paasch <cpaasch@...nai.com>
> >
> > When gso_segs is left at 0, a number of assumptions will end up being
> > incorrect throughout the stack.
> >
> > For example, in the GRO-path, we set NAPI_GRO_CB()->count to gso_segs.
> > So, if a non-LRO'ed packet followed by an LRO'ed packet is being
> > processed in GRO, the first one will have NAPI_GRO_CB()->count set to 1 and
> > the next one to 0 (in dev_gro_receive()).
> > Since commit 531d0d32de3e
> > ("net/mlx5: Correctly set gso_size when LRO is used")
> > these packets will get merged (as their gso_size now matches).
> > So, we end up in gro_complete() with NAPI_GRO_CB()->count == 1 and thus
> > don't call inet_gro_complete(). Meaning, checksum-validation in
> > tcp_checksum_complete() will fail with a "hw csum failure".
> >
> > Even before the above mentioned commit, incorrect gso_segs means that other
> > things like TCP's accounting of incoming packets (tp->segs_in,
> > data_segs_in, rcv_ooopack) will be incorrect. Which means that if one
> > does bytes_received/data_segs_in, the result will be bigger than the
> > MTU.
> >
> > Fix this by initializing gso_segs correctly when LRO is used.
> >
> > Fixes: e586b3b0baee ("net/mlx5: Ethernet Datapath files")
>
> Maybe we should put an additional Fixes line for the gso_size patch?
> It doesn't directly fix it, but it will clearly emphasize the importance
> of picking up this patch together with the other one.
>
> > Reported-by: Gal Pressman <gal@...dia.com>
> > Closes: https://lore.kernel.org/netdev/6583783f-f0fb-4fb1-a415-feec8155bc69@nvidia.com/
> > Signed-off-by: Christoph Paasch <cpaasch@...nai.com>
>
> Thanks Christoph,
> Reviewed-by: Gal Pressman <gal@...dia.com>

I do not think we need many Fixes: tag.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>

If we really want to be precise, the issue also came when GRO got
support for GRO packets ;)

commit 5eddb24901ee    gro: add support of (hw)gro packets to gro stack

This commit really implied that both gso_size and gso_segs had to be
set by drivers RX paths.

It seems drivers/net/ethernet/google/gve/gve_rx_dqo.c has a similar issue.

gve_rx_complete_rsc() sets gso_size but not gso_segs

shinfo->gso_size = le16_to_cpu(desc->rsc_seg_len);