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cirrus_vga: fix off-by-one in blit_region_is_unsafe 

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 <kraxel@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1455121059-18280-1-git-send-email-pbonzini@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Paolo Bonzini 2016-02-10 17:17:39 +01:00 committed by Gerd Hoffmann
parent 071608b519
commit d2ba7ecb34
1 changed files with 2 additions and 2 deletions
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4
hw/display/cirrus_vga.c
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@ -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;
}
}