linux-kernel - Re: BUG: core dump in selftest of proc fs

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Date:   Fri, 6 Jan 2023 14:53:11 +0100
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     linux-kselftest@...r.kernel.org, Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Brian Foster <bfoster@...hat.com>,
        Guo Zhengkui <guozhengkui@...o.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thorsten Leemhuis <regressions@...mhuis.info>
Subject: Re: BUG: core dump in selftest of proc fs

On 06. 01. 2023. 11:39, Alexey Dobriyan wrote:
> On Wed, Jan 04, 2023 at 07:27:40PM +0100, Mirsad Goran Todorovac wrote:
>> Dear all,
>>
>> Trying to complete `make kselftest` for the first time, so maybe I'm doing something wrong?
>>
>> Or we are having a regression in 6.2-rc2 release candidate ...
>>
>> However, the output of selftest run is:
>>
>> make[2]: Entering directory '.../linux_torvalds/tools/testing/selftests/proc'
>> TAP version 13
>> 1..21
>> # selftests: proc: fd-001-lookup
>> ok 1 selftests: proc: fd-001-lookup
>> # selftests: proc: fd-002-posix-eq
>> ok 2 selftests: proc: fd-002-posix-eq
>> # selftests: proc: fd-003-kthread
>> ok 3 selftests: proc: fd-003-kthread
>> # selftests: proc: proc-loadavg-001
>> ok 4 selftests: proc: proc-loadavg-001
>> # selftests: proc: proc-empty-vm
>> # proc-empty-vm: proc-empty-vm.c:184: test_proc_pid_maps: Assertion `rv == 0' failed.
>> # /usr/bin/timeout: the monitored command dumped core
>> # Aborted
>> not ok 5 selftests: proc: proc-empty-vm # exit=134
>> # selftests: proc: proc-pid-vm
>> # proc-pid-vm: proc-pid-vm.c:365: main: Assertion `rv == len' failed.
>> # /usr/bin/timeout: the monitored command dumped core
>> # Aborted
>>
>> Please find attached lshw output, dmesg, config and lsmod.
>>
>> I am available for further diagnostics.
>>
>> The platform is Ubuntu 22.10 kinetic kudu on a Lenovo Ideapad 3 15ITL6 laptop.
> 
> The "bug" is that "call rel32" instruction testing for executable
> vsyscall page which should be relocated to "call 0xffffffffff600000"
> is messed up. Ubuntu 22.10 ships with "vsyscall=xonly" so there should not be
> any faults when executing from it. But segfault happens with normal
> randomised userspace address.
> 
> I'll change it to "call *rax" which should be more robust (and works)
> and free from relocations.

If you will need to test the patch in the same environment where the problem initially
occurred, I am ready at your disposal.

Thanks,
Mirsad

--
Mirsad Goran Todorovac
Sistem inženjer
Grafički fakultet | Akademija likovnih umjetnosti
Sveučilište u Zagrebu
-- 
System engineer
Faculty of Graphic Arts | Academy of Fine Arts
University of Zagreb, Republic of Croatia
The European Union