From: Li Qiang <[email protected]> When doing bitblt copy in backward mode, we should minus the blt width first just like the adding in the forward mode. This can avoid the oob access of the front of vga's vram.
Signed-off-by: Li Qiang <[email protected]> Message-id: [email protected] { kraxel: with backward blits (negative pitch) addr is the topmost address, so check it as-is against vram size ] Cc: [email protected] Cc: P J P <[email protected]> Cc: Laszlo Ersek <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Wolfgang Bumiller <[email protected]> Fixes: d3532a0db02296e687711b8cdc7791924efccea0 (CVE-2014-8106) Signed-off-by: Gerd Hoffmann <[email protected]> --- hw/display/cirrus_vga.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c index 95873ae..3961712 100644 --- a/hw/display/cirrus_vga.c +++ b/hw/display/cirrus_vga.c @@ -277,10 +277,9 @@ static bool blit_region_is_unsafe(struct CirrusVGAState *s, } if (pitch < 0) { int64_t min = addr - + ((int64_t)s->cirrus_blt_height-1) * pitch; - int32_t max = addr - + s->cirrus_blt_width; - if (min < 0 || max > s->vga.vram_size) { + + ((int64_t)s->cirrus_blt_height - 1) * pitch + - s->cirrus_blt_width; + if (min < -1 || addr >= s->vga.vram_size) { return true; } } else { -- 1.8.3.1
