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From: "Christian König" <christian.koenig@amd.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: linux-fsdevel@vger.kernel.org, linux-mm <linux-mm@kvack.org>,
	Chengguang Xu <cgxu519@mykernel.net>,
	overlayfs <linux-unionfs@vger.kernel.org>
Subject: Re: [PATCH] ovl: fix mmap denywrite
Date: Wed, 23 Jun 2021 13:41:02 +0200	[thread overview]
Message-ID: <8d9ac67c-8e97-3f53-95b8-548a8bec6358@amd.com> (raw)
In-Reply-To: <CAJfpegvTa9wnvCBP-vHumnDQ6f3XWb5vD6Fnpjbrj1V5N8QRig@mail.gmail.com>



Am 22.06.21 um 17:10 schrieb Miklos Szeredi:
> On Tue, 22 Jun 2021 at 14:43, Christian König <christian.koenig@amd.com> wrote:
>> Am 22.06.21 um 14:30 schrieb Miklos Szeredi:
>>> Overlayfs did not honor positive i_writecount on realfile for VM_DENYWRITE
>>> mappings.  Similarly negative i_mmap_writable counts were ignored for
>>> VM_SHARED mappings.
>>>
>>> Fix by making vma_set_file() switch the temporary counts obtained and
>>> released by mmap_region().
>> Mhm, I don't fully understand the background but that looks like
>> something specific to overlayfs to me.
>>
>> So why are you changing the common helper?
> Need to hold the temporary counts until the final ones are obtained in
> vma_link(), which is out of overlayfs' scope.

Ah! So basically we need to move the denial counts which mmap_region() 
added to the original file to the new one as well. That's indeed a 
rather good point.

Can you rather change the vma_set_file() function to return the error 
and add a __must_check?

I can take care fixing the users in DMA-buf and DRM subsystem.

Thanks,
Christian.

>
> Thanks,
> Miklos


  reply	other threads:[~2021-06-23 11:41 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-22 12:30 [PATCH] ovl: fix mmap denywrite Miklos Szeredi
2021-06-22 12:43 ` Christian König
2021-06-22 15:10   ` Miklos Szeredi
2021-06-22 15:10     ` Miklos Szeredi
2021-06-23 11:41     ` Christian König [this message]
2021-07-09 13:48       ` Miklos Szeredi
2021-07-12 11:15         ` Christian König
2021-06-23  6:06 ` 回复:[PATCH] " Chengguang Xu

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