From: Li Qiang 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 Message-id: address@hidden { kraxel: with backward blits (negative pitch) addr is the topmost address, so check it as-is against vram size ] [ This is CVE-2017-2615 / XSA-208 - Ian Jackson ] Cc: address@hidden Cc: P J P Cc: Laszlo Ersek Cc: Paolo Bonzini Cc: Wolfgang Bumiller Fixes: d3532a0db02296e687711b8cdc7791924efccea0 (CVE-2014-8106) Signed-off-by: Gerd Hoffmann --- 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 bdb092e..3bbe3d5 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