From: BALATON Zoltan <balaton@eik.bme.hu>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Prasad J Pandit <pjp@fedoraproject.org>,
Yi Ren <c4tren@gmail.com>,
QEMU Developers <qemu-devel@nongnu.org>,
P J P <ppandit@redhat.com>, Ren Ding <rding@gatech.edu>,
Hanqing Zhao <hanqing@gatech.edu>
Subject: Re: [PATCH] ati-vga: increment mm_index in ati_mm_read/write
Date: Wed, 3 Jun 2020 15:56:48 +0200 (CEST) [thread overview]
Message-ID: <alpine.BSF.2.22.395.2006031554560.9760@zero.eik.bme.hu> (raw)
In-Reply-To: <20200603134404.xdb2koul7fatv4ez@sirius.home.kraxel.org>
On Wed, 3 Jun 2020, Gerd Hoffmann wrote:
> On Wed, Jun 03, 2020 at 06:17:32PM +0530, P J P wrote:
>> From: Prasad J Pandit <pjp@fedoraproject.org>
>>
>> While accessing VGA registers via ati_mm_read/write routines,
>> a guest may set 's->regs.mm_index' such that it leads to infinite
>> recursion.
>
> Lovely.
>
>> Increment the mm_index value to avoid it.
>
> Hmm, why modify mm_index? Shouldn't we just check it is non-zero
> before calling ati_mm_read/ati_mm_write?
I haven't found any mention in any docs that say MM_INDEX should auto
increment so unless this is proven to do that on real hardware I also
think forbiding indexed access to index registers should be enough.
Regards,
BALATON Zoltan
next prev parent reply other threads:[~2020-06-03 13:57 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-03 12:47 [PATCH] ati-vga: increment mm_index in ati_mm_read/write P J P
2020-06-03 13:44 ` Gerd Hoffmann
2020-06-03 13:56 ` BALATON Zoltan [this message]
2020-06-03 14:35 ` P J P
2020-06-03 15:32 ` Gerd Hoffmann
2020-06-03 15:38 ` BALATON Zoltan
2020-06-03 15:43 ` BALATON Zoltan
2020-06-03 19:08 ` P J P
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