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Subject: Re: [PATCH 1/2] mm: mmap: fix fput in error path v2
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
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 <20201106114806.46015-2-christian.koenig@amd.com>
 <20201106144811.cf228ca9278ec78887d42960@linux-foundation.org>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>
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Date:   Wed, 18 Nov 2020 11:57:44 +0100
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Am 06.11.20 um 23:48 schrieb Andrew Morton:
> On Fri,  6 Nov 2020 12:48:05 +0100 "Christian König" <ckoenig.leichtzumerken@gmail.com> wrote:
>
>> Patch "495c10cc1c0c CHROMIUM: dma-buf: restore args..."
>> adds a workaround for a bug in mmap_region.
>>
>> As the comment states ->mmap() callback can change
>> vma->vm_file and so we might call fput() on the wrong file.
>>
>> Revert the workaround and proper fix this in mmap_region.
>>
> Seems correct, best I can tell.  Presumably all ->mmap() instances will
> correctly fput() to original file* if they're rewriting vma->vm_file.

Yes, exactly.

Patch #2 provides a helper to make sure that everybody gets the 
get_file()/fput() correctly while updating vma->vm_file.

Can I add your acked-by to the patches and push them upstream through 
drm-misc-next?

Thanks,
Christian.