netdev - Re: [PATCH bpf v3 1/4] af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash

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Message-ID: <874j8yoq08.fsf@cloudflare.com>
Date: Tue, 09 Jul 2024 11:48:07 +0200
From: Jakub Sitnicki <jakub@...udflare.com>
To: Michal Luczaj <mhal@...x.co>
Cc: netdev@...r.kernel.org,  bpf@...r.kernel.org,  davem@...emloft.net,
  edumazet@...gle.com,  kuba@...nel.org,  pabeni@...hat.com,
  john.fastabend@...il.com,  kuniyu@...zon.com,  Rao.Shoaib@...cle.com,
  cong.wang@...edance.com
Subject: Re: [PATCH bpf v3 1/4] af_unix: Disable MSG_OOB handling for
 sockets in sockmap/sockhash

On Sun, Jul 07, 2024 at 11:28 PM +02, Michal Luczaj wrote:
> AF_UNIX socket tracks the most recent OOB packet (in its receive queue)
> with an `oob_skb` pointer. BPF redirecting does not account for that: when
> an OOB packet is moved between sockets, `oob_skb` is left outdated. This
> results in a single skb that may be accessed from two different sockets.
>
> Take the easy way out: silently drop MSG_OOB data targeting any socket that
> is in a sockmap or a sockhash. Note that such silent drop is akin to the
> fate of redirected skb's scm_fp_list (SCM_RIGHTS, SCM_CREDENTIALS).
>
> For symmetry, forbid MSG_OOB in unix_bpf_recvmsg().
>
> Suggested-by: Kuniyuki Iwashima <kuniyu@...zon.com>
> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
> Signed-off-by: Michal Luczaj <mhal@...x.co>
> ---

Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>