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SubjectRe: BUG selftests/mm]
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On 09.03.24 20:12, Mirsad Todorovac wrote:
> Hi,
>
> Routine run of the test in net-next gave also this mm unit error.
>
> root@defiant:tools/testing/selftests/mm# ./uffd-unit-tests
> Testing UFFDIO_API (with syscall)... done
> Testing UFFDIO_API (with /dev/userfaultfd)... done
> Testing register-ioctls on anon... done
> Testing register-ioctls on shmem... done
> Testing register-ioctls on shmem-private... done
> Testing register-ioctls on hugetlb... skipped [reason: memory allocation failed]
> Testing register-ioctls on hugetlb-private... skipped [reason: memory allocation failed]
> Testing zeropage on anon... done
> Testing zeropage on shmem... done
> Testing zeropage on shmem-private... done
> Testing zeropage on hugetlb... skipped [reason: memory allocation failed]
> Testing zeropage on hugetlb-private... skipped [reason: memory allocation failed]
> Testing move on anon... done
> Testing move-pmd on anon... done
> Testing move-pmd-split on anon... done
> Testing wp-fork on anon... done
> Testing wp-fork on shmem... done
> Testing wp-fork on shmem-private... done
> Testing wp-fork on hugetlb... skipped [reason: memory allocation failed]
> Testing wp-fork on hugetlb-private... skipped [reason: memory allocation failed]
> Testing wp-fork-with-event on anon... done
> Testing wp-fork-with-event on shmem... done
> Testing wp-fork-with-event on shmem-private... done
> Testing wp-fork-with-event on hugetlb... skipped [reason: memory allocation failed]
> Testing wp-fork-with-event on hugetlb-private... skipped [reason: memory allocation failed]
> Testing wp-fork-pin on anon... done
> Testing wp-fork-pin on shmem... done
> Testing wp-fork-pin on shmem-private... done
> Testing wp-fork-pin on hugetlb... skipped [reason: memory allocation failed]
> Testing wp-fork-pin on hugetlb-private... skipped [reason: memory allocation failed]
> Testing wp-fork-pin-with-event on anon... done
> Testing wp-fork-pin-with-event on shmem... done
> Testing wp-fork-pin-with-event on shmem-private... done
> Testing wp-fork-pin-with-event on hugetlb... skipped [reason: memory allocation failed]
> Testing wp-fork-pin-with-event on hugetlb-private... skipped [reason: memory allocation failed]
> Testing wp-unpopulated on anon... done
> Testing minor on shmem... done
> Testing minor on hugetlb... skipped [reason: memory allocation failed]
> Testing minor-wp on shmem... done
> Testing minor-wp on hugetlb... skipped [reason: memory allocation failed]
> Testing minor-collapse on shmem... done
> Testing sigbus on anon... done
> Testing sigbus on shmem... done
> Testing sigbus on shmem-private... done
> Testing sigbus on hugetlb... skipped [reason: memory allocation failed]
> Testing sigbus on hugetlb-private... skipped [reason: memory allocation failed]
> Testing sigbus-wp on anon... done
> Testing sigbus-wp on shmem... done
> Testing sigbus-wp on shmem-private... done
> Testing sigbus-wp on hugetlb... skipped [reason: memory allocation failed]
> Testing sigbus-wp on hugetlb-private... skipped [reason: memory allocation failed]
> Testing events on anon... done
> Testing events on shmem... done
> Testing events on shmem-private... done
> Testing events on hugetlb... skipped [reason: memory allocation failed]
> Testing events on hugetlb-private... skipped [reason: memory allocation failed]
> Testing events-wp on anon... done
> Testing events-wp on shmem... done
> Testing events-wp on shmem-private... done
> Testing events-wp on hugetlb... skipped [reason: memory allocation failed]
> Testing events-wp on hugetlb-private... skipped [reason: memory allocation failed]
> Testing poison on anon... done
> Testing poison on shmem... done
> Testing poison on shmem-private... done
> Testing poison on hugetlb... skipped [reason: memory allocation failed]
> Testing poison on hugetlb-private... skipped [reason: memory allocation failed]
> Userfaults unit tests: pass=42, skip=24, fail=0 (total=66)
> root@defiant:tools/testing/selftests/mm# grep -i huge /proc/meminfo
>
> It resulted in alarming errors in the syslog:
>
> Mar 9 19:48:24 defiant kernel: [77187.055103] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4631e000
> Mar 9 19:48:24 defiant kernel: [77187.055132] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46320000
> Mar 9 19:48:24 defiant kernel: [77187.055160] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46322000
> Mar 9 19:48:24 defiant kernel: [77187.055189] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46324000
> Mar 9 19:48:24 defiant kernel: [77187.055218] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46326000
> Mar 9 19:48:24 defiant kernel: [77187.055250] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46328000
> Mar 9 19:48:24 defiant kernel: [77187.055278] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4632a000
> Mar 9 19:48:24 defiant kernel: [77187.055307] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4632c000
> Mar 9 19:48:24 defiant kernel: [77187.055336] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4632e000
> Mar 9 19:48:24 defiant kernel: [77187.055366] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46330000
> Mar 9 19:48:24 defiant kernel: [77187.055395] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46332000
> Mar 9 19:48:24 defiant kernel: [77187.055423] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46334000
> Mar 9 19:48:24 defiant kernel: [77187.055452] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46336000
> Mar 9 19:48:24 defiant kernel: [77187.055480] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46338000
> Mar 9 19:48:24 defiant kernel: [77187.055509] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4633a000
> Mar 9 19:48:24 defiant kernel: [77187.055538] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4633c000
> Mar 9 19:48:24 defiant kernel: [77187.055567] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 4633e000
> Mar 9 19:48:24 defiant kernel: [77187.055597] MCE: Killing uffd-unit-tests:1321817 due to hardware memory corruption fault at 46340000
>
> At this point, it can be problem with my box's memory chips, or something with HUGETLB.
>
> However, since the "classic" allocations were successful, the problem might be in huge pages, or
> if I understood well, in deliberate poisoning of pages?
>

Isn't that just the (expected) side effect of UFFDIO_POISON tests?

IOW, there is no problem here. We are poisoning virtual memory locations
(not actual memory) and expect a SIGBUS on next access. While testing
that, we receive these messages.

The "ugly" thing here seems to be that we can trigger repeated pr_err()
from user space. There is no rate-limiting in place. Maybe UFFDIO_POISON
requires root permissions so this cannot be exploited by unprivileged
user space to flood the system log?

CCing Axel

--
Cheers,

David / dhildenb


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