Re: [Qemu-devel] [PULL 1/1] vga: fix region calculation

[Mark Kanda]

On 3/12/2018 5:59 AM, Gerd Hoffmann wrote:

Typically the scanline length and the line offset are identical.  But
in case they are not our calculation for region_end is incorrect.  Using
line_offset is fine for all scanlines, except the last one where we have
to use the actual scanline length.

Fixes: CVE-2018-7550


This doesn't appear to be the correct CVE number.

https://nvd.nist.gov/vuln/detail/CVE-2018-7550

..please confirm..

Thanks,

-Mark


Reported-by: Ross Lagerwall 
Signed-off-by: Gerd Hoffmann 
Reviewed-by: Prasad J Pandit 
Tested-by: Ross Lagerwall 
Message-id: 20180309143704.13420-1-kra...@redhat.com
---
  hw/display/vga.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 28f298b342..72181330b8 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1483,6 +1483,8 @@ static void vga_draw_graphic(VGACommonState *s, int 
full_update)
  
  region_start = (s->start_addr * 4);

  region_end = region_start + (ram_addr_t)s->line_offset * height;
+region_end += width * s->get_bpp(s) / 8; /* scanline length */
+region_end -= s->line_offset;
  if (region_end > s->vbe_size) {
  /* wraps around (can happen with cirrus vbe modes) */
  region_start = 0;

[Qemu-devel] [PULL 1/1] vga: fix region calculation

[Gerd Hoffmann]

Typically the scanline length and the line offset are identical.  But
in case they are not our calculation for region_end is incorrect.  Using
line_offset is fine for all scanlines, except the last one where we have
to use the actual scanline length.

Fixes: CVE-2018-7550
Reported-by: Ross Lagerwall 
Signed-off-by: Gerd Hoffmann 
Reviewed-by: Prasad J Pandit 
Tested-by: Ross Lagerwall 
Message-id: 20180309143704.13420-1-kra...@redhat.com
---
 hw/display/vga.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 28f298b342..72181330b8 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -1483,6 +1483,8 @@ static void vga_draw_graphic(VGACommonState *s, int 
full_update)
 
 region_start = (s->start_addr * 4);
 region_end = region_start + (ram_addr_t)s->line_offset * height;
+region_end += width * s->get_bpp(s) / 8; /* scanline length */
+region_end -= s->line_offset;
 if (region_end > s->vbe_size) {
 /* wraps around (can happen with cirrus vbe modes) */
 region_start = 0;
-- 
2.9.3