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Re: [Qemu-devel] [PATCH] cirrus_vga: fix off-by-one in blit_region_is_un


From: Paolo Bonzini
Subject: Re: [Qemu-devel] [PATCH] cirrus_vga: fix off-by-one in blit_region_is_unsafe
Date: Wed, 10 Feb 2016 16:29:44 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0


On 10/02/2016 15:55, Laszlo Ersek wrote:
>> > Hmm, not sure why.  We're comparing against the inclusive-exclusive
>> > range [0,s->vga.vram_size).  The right way to check if something is
>> > within the range is >= min && < max; the right way to check if something
>> > is outside the range is < min || >= max.
> Absolutely: if the thing you are verifying against the interval is
> itself an inclusive thing, that is, a pixel or byte *drawn*. However,
> exactly as you stated in the commit message, for the maximum check, what
> we are comparing is the first offset *not* processed.

Right, what my patch does is setting min and max both to pixels that are
drawn.

Paolo



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