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

[Michal Luczaj <mhal@rbox.co>]

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 an OOB packet is moved between sockets, `oob_skb` is left outdated.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@amazon.com>
>> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
>> Signed-off-by: Michal Luczaj <mhal@rbox.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