[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PULL 1/2] cirrus_vga: fix off-by-one in blit_region_is_uns
From: |
Gerd Hoffmann |
Subject: |
[Qemu-devel] [PULL 1/2] cirrus_vga: fix off-by-one in blit_region_is_unsafe |
Date: |
Tue, 1 Mar 2016 08:17:28 +0100 |
From: Paolo Bonzini <address@hidden>
The "max" value is being compared with >=, but addr + width points to
the first byte that will _not_ be copied. Laszlo suggested using a
"greater than" comparison, instead of subtracting one like it is
already done above for the height, so that max remains always positive.
The mistake is "safe"---it will reject some blits, but will never cause
out-of-bounds writes.
Cc: Gerd Hoffmann <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Reviewed-by: Laszlo Ersek <address@hidden>
Message-id: address@hidden
Signed-off-by: Gerd Hoffmann <address@hidden>
---
hw/display/cirrus_vga.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/display/cirrus_vga.c b/hw/display/cirrus_vga.c
index b6ce1c8..57b91a7 100644
--- a/hw/display/cirrus_vga.c
+++ b/hw/display/cirrus_vga.c
@@ -276,14 +276,14 @@ static bool blit_region_is_unsafe(struct CirrusVGAState
*s,
+ ((int64_t)s->cirrus_blt_height-1) * pitch;
int32_t max = addr
+ s->cirrus_blt_width;
- if (min < 0 || max >= s->vga.vram_size) {
+ if (min < 0 || max > s->vga.vram_size) {
return true;
}
} else {
int64_t max = addr
+ ((int64_t)s->cirrus_blt_height-1) * pitch
+ s->cirrus_blt_width;
- if (max >= s->vga.vram_size) {
+ if (max > s->vga.vram_size) {
return true;
}
}
--
1.8.3.1