linux-kernel - [ 24/49] video: mxsfb: fix crash when unblanking the display

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Message-Id: <20130113174300.852671306@decadent.org.uk>
Date:	Sun, 13 Jan 2013 17:43:19 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Lothar Waßmann <LW@...O-electronics.de>,
	Juergen Beisert <jbe@...gutronix.de>,
	Lauri Hintsala <lauri.hintsala@...egiga.net>,
	Shawn Guo <shawn.guo@...aro.org>
Subject: [ 24/49] video: mxsfb: fix crash when unblanking the display

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lothar Waßmann <LW@...O-electronics.de>

commit 6c1ecba8d84841277d68140ef485335d5be28485 upstream.

The VDCTRL4 register does not provide the MXS SET/CLR/TOGGLE feature.
The write in mxsfb_disable_controller() sets the data_cnt for the LCD
DMA to 0 which obviously means the max. count for the LCD DMA and
leads to overwriting arbitrary memory when the display is unblanked.

Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
Acked-by: Juergen Beisert <jbe@...gutronix.de>
Tested-by: Lauri Hintsala <lauri.hintsala@...egiga.net>
Signed-off-by: Shawn Guo <shawn.guo@...aro.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/video/mxsfb.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/video/mxsfb.c
+++ b/drivers/video/mxsfb.c
@@ -366,7 +366,8 @@ static void mxsfb_disable_controller(str
 		loop--;
 	}
 
-	writel(VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4 + REG_CLR);
+	reg = readl(host->base + LCDC_VDCTRL4);
+	writel(reg & ~VDCTRL4_SYNC_SIGNALS_ON, host->base + LCDC_VDCTRL4);
 
 	clk_disable(host->clk);
 


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