linux-kernel - Re: selftests: net/af_unix test_unix

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Message-ID: <a62aa114-8322-6d93-4388-502896941bf2@alu.unizg.hr>
Date:   Sun, 20 Aug 2023 12:34:27 +0200
From:   Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>
Cc:     alexander@...alicyn.com, davem@...emloft.net, edumazet@...gle.com,
        fw@...len.de, kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        pabeni@...hat.com, shuah@...nel.org
Subject: Re: selftests: net/af_unix test_unix_oob [FAILED][NEW]

On 8/14/23 10:54, Mirsad Todorovac wrote:
> On 8/8/23 10:53, Mirsad Todorovac wrote:
>> On 8/8/23 01:09, Mirsad Todorovac wrote:
>>> On 8/7/23 22:46, Kuniyuki Iwashima wrote:
>>>> From: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
>>>> Date: Mon, 7 Aug 2023 21:44:41 +0200
>>>>> Hi all,
>>>>>
>>>>> In the kernel 6.5-rc5 build on Ubuntu 22.04 LTS (jammy jellyfish) on a Ryzen 7950 assembled box,
>>>>> vanilla torvalds tree kernel, the test test_unix_oob unexpectedly fails:
>>>>>
>>>>> # selftests: net/af_unix: test_unix_oob
>>>>> # Test 2 failed, sigurg 23 len 63 OOB %
>>>>>
>>>>> It is this code:
>>>>>
>>>>>           /* Test 2:
>>>>>            * Verify that the first OOB is over written by
>>>>>            * the 2nd one and the first OOB is returned as
>>>>>            * part of the read, and sigurg is received.
>>>>>            */
>>>>>           wait_for_data(pfd, POLLIN | POLLPRI);
>>>>>           len = 0;
>>>>>           while (len < 70)
>>>>>                   len = recv(pfd, buf, 1024, MSG_PEEK);
>>>>>           len = read_data(pfd, buf, 1024);
>>>>>           read_oob(pfd, &oob);
>>>>>           if (!signal_recvd || len != 127 || oob != '#') {
>>>>>                   fprintf(stderr, "Test 2 failed, sigurg %d len %d OOB %c\n",
>>>>>                   signal_recvd, len, oob);
>>>>>                   die(1);
>>>>>           }
>>>>>
>>>>> In 6.5-rc4, this test was OK, so it might mean we have a regression?
>>>>
>>>> Thanks for reporting.
>>>>
>>>> I confirmed the test doesn't fail on net-next at least, but it's based
>>>> on v6.5-rc4.
>>>>
>>>>    ---8<---
>>>>    [root@...alhost ~]# ./test_unix_oob
>>>>    [root@...alhost ~]# echo $?
>>>>    0
>>>>    [root@...alhost ~]# uname -r
>>>>    6.5.0-rc4-01192-g66244337512f
>>>>    ---8<---
>>>>
>>>> I'll check 6.5-rc5 later.
>>>
>>> Hi, Kuniyuki,
>>>
>>> It seems that there is a new development. I could reproduce the error with the failed test 2
>>> as early as 6.0-rc1. However, the gotcha is that the error appears to be sporadically manifested
>>> (possibly a race)?
>>>
>>> I am currently attempting a bisect.
>>
>> Bisect had shown that the condition existed already at 5.11 torvalds tree.
>>
>> It has to do with the configs chosen (I used the configs from seltests/*/config merged), but it
>> is also present in the Ubuntu production build:
>>
>> marvin@...iant:~$ cd linux/kernel/linux_torvalds
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> Test 2 failed, sigurg 23 len 63 OOB %
>> marvin@...iant:~/linux/kernel/linux_torvalds$ uname -rms
>> Linux 6.4.8-060408-generic x86_64
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> Test 1 failed sigurg 0 len 63
>> marvin@...iant:~/linux/kernel/linux_torvalds$
>>
>> It happens on rare occasions, so it seems to be a hard-to-spot race.
>>
>> Normal test running test_unix_oob once never noticed that, save by accident, which brought the problem to attention ...
>>
>> However, the problem seems to be config-driven rather than kernel-version-driven.
>>
>> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..100000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
>> Test 3.1 Inline failed, len 1 oob % atmark 0
>> Test 1 Inline failed, sigurg 0 len 63
>> Test 1 Inline failed, sigurg 0 len 63
>> Test 1 Inline failed, sigurg 0 len 63
>> Test 2 Inline failed, len 63 atmark 1
>> Test 3 Inline failed, sigurg 23 len 63 data x
>> Test 3 Inline failed, sigurg 23 len 63 data x
>> Test 3 Inline failed, sigurg 23 len 63 data x
>> Test 3 Inline failed, sigurg 23 len 63 data x
>> Test 2 Inline failed, len 63 atmark 1
>> Test 3.1 Inline failed, len 1 oob % atmark 0
>> Test 2 failed, sigurg 23 len 63 OOB %
>> marvin@...iant:~/linux/kernel/linux_torvalds$ uname -rms
>> Linux 6.5.0-060500rc4-generic x86_64
>> marvin@...iant:~/linux/kernel/linux_torvalds$
>>
>> At moments, I was able to reproduce with certain configs, but now something odd happens.
>>
>> I will keep investigating.
> 
> Please not that the bug persisted in 6.5-rc6:
> 
> marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..100000}; do !!; done
> for a in {0..100000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
> Test 2 failed, sigurg 23 len 63 OOB %
> Test 2 Inline failed, len 63 atmark 1
> Test 3 Inline failed, sigurg 23 len 63 data x
> Test 2 failed, sigurg 23 len 63 OOB %
> Test 3.1 Inline failed, len 1 oob % atmark 0
> Test 3 Inline failed, sigurg 23 len 63 data x
> Test 1 Inline failed, sigurg 0 len 63
> Test 1 Inline failed, sigurg 0 len 63
> Test 3.1 Inline failed, len 1 oob % atmark 0
> Test 1 Inline failed, sigurg 0 len 63
> Test 2 failed, sigurg 23 len 63 OOB %
> Test 1 Inline failed, sigurg 0 len 63
> Test 2 failed, sigurg 23 len 63 OOB %
> Test 3.1 Inline failed, len 1 oob % atmark 0
> Test 3.1 Inline failed, len 1 oob % atmark 0
> marvin@...iant:~/linux/kernel/linux_torvalds$
> 
> The bug can be triggered as a non-privileged user, but is not clear whether it is exploitable to elevate privileges.

Hi again,

I have tried the selftests/net/af_unix/test_oob_unix and:

marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 1 Inline failed, sigurg 0 len 63
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 failed, sigurg 23 len 63 OOB %
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 failed, sigurg 23 len 63 OOB %
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 3 Inline failed, sigurg 23 len 63 data x
Test 1 Inline failed, sigurg 0 len 63
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 1 Inline failed, sigurg 0 len 63
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 1 Inline failed, sigurg 0 len 63
Test 1 Inline failed, sigurg 0 len 63
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 failed, sigurg 23 len 63 OOB %
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 1 Inline failed, sigurg 0 len 63
Test 1 Inline failed, sigurg 0 len 63
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3 Inline failed, sigurg 23 len 63 data x
Test 1 Inline failed, sigurg 0 len 63
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 1 Inline failed, sigurg 0 len 63
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 failed, sigurg 23 len 63 OOB %
Test 2 failed, sigurg 23 len 63 OOB %
marvin@...iant:~/linux/kernel/linux_torvalds$

The kernel is 6.5.0-rc6-net-cfg-kcsan-00038-g16931859a650 vanilla torvalds tree on Ubuntu 22.04.

Best regards,
Mirsad Todorovac
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