linux-kernel - Re: [xdp-hints] [PATCH bpf RFC-V2 1/5] xdp: rss hash types representation

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] [day] [month] [year] [list]

Message-ID: <87355nnsdb.fsf@toke.dk>
Date:   Wed, 29 Mar 2023 23:46:08 +0200
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>, bpf@...r.kernel.org,
        Stanislav Fomichev <sdf@...gle.com>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, martin.lau@...nel.org,
        ast@...nel.org, daniel@...earbox.net, alexandr.lobakin@...el.com,
        larysa.zaremba@...el.com, xdp-hints@...-project.net,
        anthony.l.nguyen@...el.com, yoong.siang.song@...el.com,
        boon.leong.ong@...el.com, intel-wired-lan@...ts.osuosl.org,
        pabeni@...hat.com, jesse.brandeburg@...el.com, kuba@...nel.org,
        edumazet@...gle.com, john.fastabend@...il.com, hawk@...nel.org,
        davem@...emloft.net
Subject: Re: [xdp-hints] [PATCH bpf RFC-V2 1/5] xdp: rss hash types
 representation

Jesper Dangaard Brouer <brouer@...hat.com> writes:

> diff --git a/net/core/xdp.c b/net/core/xdp.c
> index 7133017bcd74..81d41df30695 100644
> --- a/net/core/xdp.c
> +++ b/net/core/xdp.c
> @@ -721,12 +721,14 @@ __bpf_kfunc int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx, u64 *tim
>   * @hash: Return value pointer.
>   *
>   * Return:
> - * * Returns 0 on success or ``-errno`` on error.
> + * * Returns (positive) RSS hash **type** on success or ``-errno`` on error.

This change is going to break any BPF program that does:

if (!bpf_xdp_metadata_rx_hash(ctx, &hash))
  /* do something with hash */


so I think adding a second argument is better; that way, at least
breakage will be explicit instead of being a hidden change in semantics
(and the CO-RE style checking for kfuncs Alexei introduced should
trigger correctly).

But really, what we should do anyway is merge this during the -rc phase
to minimise any breakage :)

-Toke