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Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-20
From: |
Philippe Mathieu-Daudé |
Subject: |
Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638) |
Date: |
Mon, 6 Sep 2021 20:19:34 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 |
(Forgot to Cc Alex for eventual reproducer)
On 9/6/21 6:44 PM, Mauro Matteo Cascella wrote:
> On Mon, Sep 6, 2021 at 5:31 PM Philippe Mathieu-Daudé <philmd@redhat.com>
> wrote:
>>
>> When building QEMU with DEBUG_ATI defined then running with
>> '-device ati-vga,romfile="" -d unimp,guest_errors -trace ati\*'
>> we get:
>>
>> ati_mm_write 4 0x16c0 DP_CNTL <- 0x1
>> ati_mm_write 4 0x146c DP_GUI_MASTER_CNTL <- 0x2
>> ati_mm_write 4 0x16c8 DP_MIX <- 0xff0000
>> ati_mm_write 4 0x16c4 DP_DATATYPE <- 0x2
>> ati_mm_write 4 0x224 CRTC_OFFSET <- 0x0
>> ati_mm_write 4 0x142c DST_PITCH_OFFSET <- 0xfe00000
>> ati_mm_write 4 0x1420 DST_Y <- 0x3fff
>> ati_mm_write 4 0x1410 DST_HEIGHT <- 0x3fff
>> ati_mm_write 4 0x1588 DST_WIDTH_X <- 0x3fff3fff
>> ati_2d_blt: vram:0x7fff5fa00000 addr:0 ds:0x7fff61273800 stride:2560
>> bpp:32 rop:0xff
>> ati_2d_blt: 0 0 0, 0 127 0, (0,0) -> (16383,16383) 16383x16383 > ^
>> ati_2d_blt: pixman_fill(dst:0x7fff5fa00000, stride:254, bpp:8, x:16383,
>> y:16383, w:16383, h:16383, xor:0xff000000)
>> Thread 3 "qemu-system-i38" received signal SIGSEGV, Segmentation fault.
>> (gdb) bt
>> #0 0x00007ffff7f62ce0 in sse2_fill.lto_priv () at /lib64/libpixman-1.so.0
>> #1 0x00007ffff7f09278 in pixman_fill () at /lib64/libpixman-1.so.0
>> #2 0x0000555557b5a9af in ati_2d_blt (s=0x631000028800) at
>> hw/display/ati_2d.c:196
>> #3 0x0000555557b4b5a2 in ati_mm_write (opaque=0x631000028800, addr=5512,
>> data=1073692671, size=4) at hw/display/ati.c:843
>> #4 0x0000555558b90ec4 in memory_region_write_accessor (mr=0x631000039cc0,
>> addr=5512, ..., size=4, ...) at softmmu/memory.c:492
>>
>> Commit 584acf34cb0 ("ati-vga: Fix reverse bit blts") introduced
>> the local dst_x and dst_y which adjust the (x, y) coordinates
>> depending on the direction in the SRCCOPY ROP3 operation, but
>> forgot to address the same issue for the PATCOPY, BLACKNESS and
>> WHITENESS operations, which also call pixman_fill().
>>
>> Fix that now by using the adjusted coordinates in the pixman_fill
>> call, and update the related debug printf().
>>
>> Reported-by: Qiang Liu <qiangliu@zju.edu.cn>
>> Fixes: 584acf34cb0 ("ati-vga: Fix reverse bit blts")
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>> hw/display/ati_2d.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/hw/display/ati_2d.c b/hw/display/ati_2d.c
>> index 4dc10ea7952..692bec91de4 100644
>> --- a/hw/display/ati_2d.c
>> +++ b/hw/display/ati_2d.c
>> @@ -84,7 +84,7 @@ void ati_2d_blt(ATIVGAState *s)
>> DPRINTF("%d %d %d, %d %d %d, (%d,%d) -> (%d,%d) %dx%d %c %c\n",
>> s->regs.src_offset, s->regs.dst_offset, s->regs.default_offset,
>> s->regs.src_pitch, s->regs.dst_pitch, s->regs.default_pitch,
>> - s->regs.src_x, s->regs.src_y, s->regs.dst_x, s->regs.dst_y,
>> + s->regs.src_x, s->regs.src_y, dst_x, dst_y,
>> s->regs.dst_width, s->regs.dst_height,
>> (s->regs.dp_cntl & DST_X_LEFT_TO_RIGHT ? '>' : '<'),
>> (s->regs.dp_cntl & DST_Y_TOP_TO_BOTTOM ? 'v' : '^'));
>> @@ -180,11 +180,11 @@ void ati_2d_blt(ATIVGAState *s)
>> dst_stride /= sizeof(uint32_t);
>> DPRINTF("pixman_fill(%p, %d, %d, %d, %d, %d, %d, %x)\n",
>> dst_bits, dst_stride, bpp,
>> - s->regs.dst_x, s->regs.dst_y,
>> + dst_x, dst_y,
>> s->regs.dst_width, s->regs.dst_height,
>> filler);
>> pixman_fill((uint32_t *)dst_bits, dst_stride, bpp,
>> - s->regs.dst_x, s->regs.dst_y,
>> + dst_x, dst_y,
>> s->regs.dst_width, s->regs.dst_height,
>> filler);
>> if (dst_bits >= s->vga.vram_ptr + s->vga.vbe_start_addr &&
>> --
>> 2.31.1
>>
>
> Tested-by: Mauro Matteo Cascella <mcascell@redhat.com>
Thanks. I wouldn't be surprise if we get another CVE in this code /
file / function ASAP this patch get merged... The code calls for a
rewrite, as per this function comment in its header:
void ati_2d_blt(ATIVGAState *s)
{
/* FIXME it is probably more complex than this and may need to be */
/* rewritten but for now as a start just to get some output: */
Regards,
Phil.
- [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/06
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Mauro Matteo Cascella, 2021/09/06
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638),
Philippe Mathieu-Daudé <=
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), BALATON Zoltan, 2021/09/06
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/07
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/07
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Mauro Matteo Cascella, 2021/09/09
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/09
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Alexander Bulekov, 2021/09/06
- Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/07
Re: [PATCH] hw/display/ati_2d: Fix buffer overflow in ati_2d_blt (CVE-2021-3638), Philippe Mathieu-Daudé, 2021/09/07