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

[Das, Nirmoy]

On 1/18/2023 11:26 AM, Mirsad Todorovac wrote:
> Hi,
>
> On 1/18/23 10:19, Tvrtko Ursulin wrote:
>
>> Thanks for working on this, it looks good to me and it aligns with 
>> how i915 uses the facility.
>>
>> 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!


Nirmoy

>
> Will post you if there are any changes.
>
> Regards,
> Mirsad
>