netdev - Re: [PATCH v2 net-next] virtio_net: Improve RSS key size validation and use NETDEV_RSS_KEY

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: <20260207045416-mutt-send-email-mst@kernel.org>
Date: Sat, 7 Feb 2026 04:56:13 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Srujana Challa <schalla@...vell.com>, netdev@...r.kernel.org,
	virtualization@...ts.linux.dev, pabeni@...hat.com,
	jasowang@...hat.com, xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com, davem@...emloft.net, edumazet@...gle.com,
	ndabilpuram@...vell.com, kshankar@...vell.com
Subject: Re: [PATCH v2 net-next] virtio_net: Improve RSS key size validation
 and use NETDEV_RSS_KEY_LEN

On Fri, Feb 06, 2026 at 07:13:08PM -0800, Jakub Kicinski wrote:
> On Fri, 6 Feb 2026 17:31:54 +0530 Srujana Challa wrote:
> > Replace hardcoded RSS max key size limit with NETDEV_RSS_KEY_LEN to
> > align with kernel's standard RSS key length. Add validation for RSS
> > key size against spec minimum (40 bytes) and driver maximum. When
> > validation fails, gracefully disable RSS features and continue
> > initialization rather than failing completely.
> 
> Hm, FWIW clang says:
> 
> drivers/net/virtio_net.c:6841:31: warning: result of comparison of constant 256 with expression of type 'u8' (aka 'unsigned char') is always false [-Wtautological-constant-out-of-range-compare]
>  6841 |                 } else if (vi->rss_key_size > VIRTIO_NET_RSS_MAX_KEY_SIZE) {
>       |                            ~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Which is kinda annoying because the value was increased in net-next.
> If Machael wants this backported then we need to keep the check
> and follow up in net-next? We could try to cast the u32 away but
> that feels dirty..


I'd say yes. the warning is harmless.
so
patch 1 - this code
patch 2 - replace with BUILD_BUG_ON

but i ask then whether this code was actually tested against net-next.

-- 
MST