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@xxxxxxxxxxxx>
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@localhost ~]# ./test_unix_oob
[root@localhost ~]# echo $?
0
[root@localhost ~]# uname -r
6.5.0-rc4-01192-g66244337512f
---8<---
I'll check 6.5-rc5 later.
Hi, Kuniyuki,
It seems that there is a new development. I could reproduce the error with the failed test 2
as early as 6.0-rc1. However, the gotcha is that the error appears to be sporadically manifested
(possibly a race)?
I am currently attempting a bisect.
Bisect had shown that the condition existed already at 5.11 torvalds tree.
It has to do with the configs chosen (I used the configs from seltests/*/config merged), but it
is also present in the Ubuntu production build:
marvin@defiant:~$ cd linux/kernel/linux_torvalds
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/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@defiant:~/linux/kernel/linux_torvalds$ uname -rms
Linux 6.4.8-060408-generic x86_64
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@defiant:~/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@defiant:~/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@defiant:~/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@defiant:~/linux/kernel/linux_torvalds$ uname -rms
Linux 6.5.0-060500rc4-generic x86_64
marvin@defiant:~/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@defiant:~/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@defiant:~/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.
Best regards,
Mirsad Todorovac
