[Intel-gfx] [PATCH 2/2] drm/i915: Fix a memory leak with reused mmap_offset

[Mirsad Goran Todorovac]

On 18. 01. 2023. 11:39, Das, Nirmoy wrote:
>>>
>>> Copying Mirsad who reported the issue in case he is still happy to give it a quick test. Mirsad, I don't know if you are subscribed to one of the two mailing lists where series was posted. In case not, you can grab both patches from https://patchwork.freedesktop.org/series/112952/.
>>>
>>> Nirmoy - we also have an IGT written by Chuansheng - https://patchwork.freedesktop.org/patch/515720/?series=101035&rev=4. A more generic one could be placed in gem_mmap_offset test but this one works too in my testing and is IMO better than nothing.
>>>
>>> Finally, let me add some tags below:
>>>
>>> On 17/01/2023 17:52, Nirmoy Das wrote:
>>>> drm_vma_node_allow() and drm_vma_node_revoke() should be called in
>>>> balanced pairs. We call drm_vma_node_allow() once per-file everytime a
>>>> user calls mmap_offset, but only call drm_vma_node_revoke once per-file
>>>> on each mmap_offset. As the mmap_offset is reused by the client, the
>>>> per-file vm_count may remain non-zero and the rbtree leaked.
>>>>
>>>> Call drm_vma_node_allow_once() instead to prevent that memory leak.
>>>>
>>>> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
>>>> Cc: Andi Shyti <andi.shyti at linux.intel.com>
>>>
>>> Fixes: 786555987207 ("drm/i915/gem: Store mmap_offsets in an rbtree rather than a plain list")
>>> Reported-by: Chuansheng Liu <chuansheng.liu at intel.com>
>>> Reported-by: Mirsad Todorovac <mirsad.todorovac at alu.unizg.hr>
>>> Cc: <stable at vger.kernel.org> # v5.7+
>>> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>>
>>> Regards,
>>>
>>> Tvrtko
>>>
>>>>
>>>> Signed-off-by: Nirmoy Das <nirmoy.das at intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>>> index 4f69bff63068..2aac6bf78740 100644
>>>> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
>>>> @@ -697,7 +697,7 @@ mmap_offset_attach(struct drm_i915_gem_object *obj,
>>>>       GEM_BUG_ON(lookup_mmo(obj, mmap_type) != mmo);
>>>>   out:
>>>>       if (file)
>>>> -        drm_vma_node_allow(&mmo->vma_node, file);
>>>> +        drm_vma_node_allow_once(&mmo->vma_node, file);
>>>>       return mmo;
>>>>   err:
>>
>> The drm/i915 patch seems OK and there are currently no memory leaks as of
>> reported by /sys/kernel/debug/kmemleak under the same Chrome load that triggered
>> the initial bug ...
> 
> 
> Thanks, Mirsad for quickly checking this!

P.S.

Dear Nirmoy,

To let me explain, as I work on the Academy of Fine Arts and the Faculty of Graphic Arts,
video and multimedia drivers are of my special interest, so I kinda enjoyed this one.

No need to thank. ;-)

In case of more bugs discovered, I will be glad to test on my available platforms,
considering it a part of my research. I can justify time spent on graphic and multimedia
drivers, so it is not a big deal.

Regards,
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