From: malc <av1474@comtv.ru>
To: Avi Kivity <avi@redhat.com>
Cc: Anthony Liguori <anthony@codemonkey.ws>,
qemu-devel@nongnu.org, Jan Kiszka <jan.kiszka@siemens.com>,
kvm@vger.kernel.org
Subject: Re: [Qemu-devel] [PATCH] memory: use signed arithmetic
Date: Wed, 3 Aug 2011 01:15:58 +0400 (MSD) [thread overview]
Message-ID: <alpine.LNX.2.00.1108030115040.3886@linmac> (raw)
In-Reply-To: <1312318249-7011-1-git-send-email-avi@redhat.com>
On Tue, 2 Aug 2011, Avi Kivity wrote:
> When trying to map an alias of a ram region, where the alias starts at
> address A and we map it into address B, and A > B, we had an arithmetic
> underflow. Because we use unsigned arithmetic, the underflow converted
> into a large number which failed addrrange_intersects() tests.
>
> The concrete example which triggered this was cirrus vga mapping
> the framebuffer at offsets 0xc0000-0xc7fff (relative to the start of
> the framebuffer) into offsets 0xa0000 (relative to system addres space
> start).
>
> With our favorite analogy of a windowing system, this is equivalent to
> dragging a subwindow off the left edge of the screen, and failing to clip
> it into its parent window which is on screen.
>
> Fix by switching to signed arithmetic.
http://stackoverflow.com/questions/3679047/integer-overflow-in-c-standards-and-compilers
In other words UB land
[..snip..]
--
mailto:av1474@comtv.ru
next prev parent reply other threads:[~2011-08-02 21:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-02 20:50 [PATCH] memory: use signed arithmetic Avi Kivity
2011-08-02 21:15 ` malc [this message]
2011-08-02 21:21 ` [Qemu-devel] " Avi Kivity
2011-08-02 21:59 ` Richard Henderson
2011-08-02 22:06 ` Avi Kivity
2011-08-02 22:15 ` Richard Henderson
2011-08-03 8:26 ` Avi Kivity
2011-08-03 11:48 ` Benjamin Herrenschmidt
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