netdev - Re: [PATCH bpf v2] af_unix: Disable MSG_OOB handling for sockets in sockmap/sockhash

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Date: Wed, 26 Jun 2024 12:19:01 +0200
From: Michal Luczaj <mhal@...x.co>
To: Jakub Sitnicki <jakub@...udflare.com>
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 <cong.wang@...edance.com>
Subject: Re: [PATCH bpf v2] af_unix: Disable MSG_OOB handling for sockets in
 sockmap/sockhash

On 6/24/24 16:15, Jakub Sitnicki wrote:
> On Sun, Jun 23, 2024 at 12:25 AM +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 an OOB packet is moved between sockets, `oob_skb` is left outdated.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>
>> ---
> 
> [+CC Cong who authored ->read_skb]
> 
> I'm guessing you have a test program that you're developing the fix
> against. Would you like to extend the test case for sockmap redirect
> from unix stream [1] to incorporate it?
> 
> Sadly unix_inet_redir_to_connected needs a fix first because it
> hardcodes sotype to SOCK_DGRAM.

Ugh, my last two replies got silently dropped by vger. Is there any way to
tell what went wrong?

So, again, sure, I'll extend the sockmap redirect test.

And regarding Rao's comment, I took a look and I think sockmap'ed TCP OOB
does indeed act the same way. I'll try to add that into selftest as well.

Thanks,
Michal