netdev - Re: [PATCH net] af_unix: Support POLLPRI for OOB.

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Date:   Mon, 14 Mar 2022 11:10:45 -0700
From:   Shoaib Rao <rao.shoaib@...cle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] af_unix: Support POLLPRI for OOB.


On 3/14/22 10:42, Eric Dumazet wrote:
>
> On 3/13/22 22:21, Kuniyuki Iwashima wrote:
>> The commit 314001f0bf92 ("af_unix: Add OOB support") introduced OOB for
>> AF_UNIX, but it lacks some changes for POLLPRI.  Let's add the missing
>> piece.
>>
>> In the selftest, normal datagrams are sent followed by OOB data, so this
>> commit replaces `POLLIN | POLLPRI` with just `POLLPRI` in the first test
>> case.
>>
>> Fixes: 314001f0bf92 ("af_unix: Add OOB support")
>> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
>> ---
>>   net/unix/af_unix.c                                  | 2 ++
>>   tools/testing/selftests/net/af_unix/test_unix_oob.c | 6 +++---
>>   2 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
>> index c19569819866..711d21b1c3e1 100644
>> --- a/net/unix/af_unix.c
>> +++ b/net/unix/af_unix.c
>> @@ -3139,6 +3139,8 @@ static __poll_t unix_poll(struct file *file, 
>> struct socket *sock, poll_table *wa
>>           mask |= EPOLLIN | EPOLLRDNORM;
>>       if (sk_is_readable(sk))
>>           mask |= EPOLLIN | EPOLLRDNORM;
>> +    if (unix_sk(sk)->oob_skb)
>> +        mask |= EPOLLPRI;
>
>
> This adds another data-race, maybe add something to avoid another 
> syzbot report ?

It's not obvious to me how there would be a race as it is just a check.

Also this change should be under #if IS_ENABLED(CONFIG_AF_UNIX_OOB)

Thanks,

Shoaib

>
>
>>         /* Connection-based need to check for termination and startup */
>>       if ((sk->sk_type == SOCK_STREAM || sk->sk_type == 
>> SOCK_SEQPACKET) &&
>> diff --git a/tools/testing/selftests/net/af_unix/test_unix_oob.c 
>> b/tools/testing/selftests/net/af_unix/test_unix_oob.c
>> index 3dece8b29253..b57e91e1c3f2 100644
>> --- a/tools/testing/selftests/net/af_unix/test_unix_oob.c
>> +++ b/tools/testing/selftests/net/af_unix/test_unix_oob.c
>> @@ -218,10 +218,10 @@ main(int argc, char **argv)
>>         /* Test 1:
>>        * veriyf that SIGURG is
>> -     * delivered and 63 bytes are
>> -     * read and oob is '@'
>> +     * delivered, 63 bytes are
>> +     * read, oob is '@', and POLLPRI works.
>>        */
>> -    wait_for_data(pfd, POLLIN | POLLPRI);
>> +    wait_for_data(pfd, POLLPRI);
>>       read_oob(pfd, &oob);
>>       len = read_data(pfd, buf, 1024);
>>       if (!signal_recvd || len != 63 || oob != '@') {