Re: XFS check crash (WAS Re: [PATCH v11 1/4] kasan: support backing vmalloc space with real shadow memory)

Daniel Axtens
2019-11-29T15:50:50Z

>>>>>
>>>>> Nope, it's vm_map_ram() not being handled
>>>>
>>>>
>>>> Another suspicious one. Related to kasan/vmalloc?
>>>
>>> Very likely the same as with ion:
>>>
>>> # git grep vm_map_ram|grep xfs
>>> fs/xfs/xfs_buf.c: * vm_map_ram() will allocate auxiliary structures (e.g.
>>> fs/xfs/xfs_buf.c: bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
>>
>> Aaargh, that's an embarassing miss.
>>
>> It's a bit intricate because kasan_vmalloc_populate function is
>> currently set up to take a vm_struct not a vmap_area, but I'll see if I
>> can get something simple out this evening - I'm away for the first part
>> of next week.

For crashes in XFS, binder etc that implicate vm_map_ram, see:
https://lore.kernel.org/linux-mm/20191129154519.30964-1-dja@axtens.net/

The easiest way I found to repro the bug is
sudo modprobe i915 mock_selftest=-1

For lock warns, one that goes through the percpu alloc path, the patch
is already queued in mmots.

For Dmitry's latest one where there's an allocation in the
purge_vmap_area_lazy path that triggers a locking warning, you'll have
to wait until next week, sorry.

Regards,
Daniel