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Re: [PATCH v2] ati-vga: check mm_index before recursive call
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH v2] ati-vga: check mm_index before recursive call |
Date: |
Thu, 4 Jun 2020 09:45:36 +0100 |
User-agent: |
Mutt/1.13.4 (2020-02-15) |
On Thu, Jun 04, 2020 at 12:25:22AM +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. Check mm_index value to avoid it.
So this is a denial of service security issue. Is there any CVE
assigned for this ?
> Reported-by: Ren Ding <rding@gatech.edu>
> Reported-by: Hanqing Zhao <hanqing@gatech.edu>
> Reported-by: Yi Ren <c4tren@gmail.com>
> Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
> ---
> hw/display/ati.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> Update v2: add check before recursive call
> -> https://lists.gnu.org/archive/html/qemu-devel/2020-06/msg00781.html
>
> diff --git a/hw/display/ati.c b/hw/display/ati.c
> index 065f197678..bda4a2d816 100644
> --- a/hw/display/ati.c
> +++ b/hw/display/ati.c
> @@ -285,7 +285,7 @@ static uint64_t ati_mm_read(void *opaque, hwaddr addr,
> unsigned int size)
> if (idx <= s->vga.vram_size - size) {
> val = ldn_le_p(s->vga.vram_ptr + idx, size);
> }
> - } else {
> + } else if (s->regs.mm_index > MM_DATA + 3) {
> val = ati_mm_read(s, s->regs.mm_index + addr - MM_DATA, size);
> }
> break;
> @@ -520,7 +520,7 @@ static void ati_mm_write(void *opaque, hwaddr addr,
> if (idx <= s->vga.vram_size - size) {
> stn_le_p(s->vga.vram_ptr + idx, size, data);
> }
> - } else {
> + } else if (s->regs.mm_index > MM_DATA + 3) {
> ati_mm_write(s, s->regs.mm_index + addr - MM_DATA, data, size);
> }
> break;
> --
> 2.26.2
>
>
Regards,
Daniel
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