Re: [PATCH] ati-vga: Do not allow unaligned access via index register

From: Alexander Bulekov <alxndr@bu.edu>
To: BALATON Zoltan <balaton@eik.bme.hu>
Cc: qemu-devel@nongnu.org, Gerd Hoffmann <kraxel@redhat.com>
Subject: Re: [PATCH] ati-vga: Do not allow unaligned access via index register
Date: Sat, 16 May 2020 10:47:14 -0400	[thread overview]
Message-ID: <20200516144706.zz54mgs7k7anq3cj@mozz.bu.edu> (raw)
In-Reply-To: <20200516132352.39E9374594E@zero.eik.bme.hu>

On 200516 1513, BALATON Zoltan wrote:
> According to docs bits 1 and 0 of MM_INDEX are hard coded to 0 so
> unaligned access via this register should not be possible.
> This also fixes problems reported in bug #1878134.
> 
> Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
> ---

Hi Zoltan,
I applied this patch and confirmed that I cannot reproduce the crash in #1878134
Thanks!

Acked-by: Alexander Bulekov <alxndr@bu.edu>

>  hw/display/ati.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/display/ati.c b/hw/display/ati.c
> index f4c4542751..2ee23173b2 100644
> --- a/hw/display/ati.c
> +++ b/hw/display/ati.c
> @@ -531,7 +531,7 @@ static void ati_mm_write(void *opaque, hwaddr addr,
>      }
>      switch (addr) {
>      case MM_INDEX:
> -        s->regs.mm_index = data;
> +        s->regs.mm_index = data & ~3;
>          break;
>      case MM_DATA ... MM_DATA + 3:
>          /* indexed access to regs or memory */
> -- 
> 2.21.3
> 
> 