linux-kernel - Re: [PATCH] framebuffer: fix screen corruption when copying

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Message-ID: <542A88DE.6080301@ti.com>
Date:	Tue, 30 Sep 2014 13:41:34 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Mikulas Patocka <mpatocka@...hat.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>
CC:	<linux-fbdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] framebuffer: fix screen corruption when copying

On 16/09/14 19:38, Mikulas Patocka wrote:
> The function bitcpy_rev has a bug that may result in screen corruption.
> The bug happens under these conditions:
> * the end of the destination area of a copy operation is aligned on a long
>   word boundary
> * the end of the source area is not aligned on a long word boundary
> * we are copying more than one long word
> 
> In this case, the variable shift is non-zero and the variable first is
> zero. The statements FB_WRITEL(comp(d0, FB_READL(dst), first), dst) reads
> the last long word of the destination and writes it back unchanged
> (because first is zero). Correctly, we should write the variable d0 to the
> last word of the destination in this case.
> 
> This patch fixes the bug by introducing and extra test if first is zero.
> 
> The patch also removes the references to fb_memmove in the code that is
> commented out because fb_memmove was removed from framebuffer subsystem.

Thanks, queued for 3.18.

 Tomi



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