linux-kernel - Re: omapdss: Division by zero in kernel

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Date:	Tue, 28 Jul 2015 13:56:02 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Tomi Valkeinen <tomi.valkeinen@...com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Jyri Sarha <jsarha@...com>
Cc:	linux-omap@...r.kernel.org, linux-fbdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Pavel Machek <pavel@....cz>,
	Sebastian Reichel <sre@...nel.org>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	Tony Lindgren <tony@...mide.com>, Nishanth Menon <nm@...com>
Subject: Re: omapdss: Division by zero in kernel

On Friday 24 July 2015 18:03:42 Pali Rohár wrote:
> Hello,
> 
> when on N900 (real HW or qemu) I run this command
> 
> / # echo 0 > /sys/devices/platform/omapdss/overlay0/enabled && echo 0 > /sys/class/graphics/fb0/size
> 
> then kernel crash with this error message
> 
> / # [   29.904113] Division by zero in kernel.
> ** 3375 printk messages dropped ** [   29.963836] [<c01e0008>] (__aeabi_uidivmod) from [<c022071c>] 
> (cfb_imageblit+0xac/0x464)
> ** 8426 printk messages dropped ** [   30.111083] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 8380 printk messages dropped ** [   30.258209] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 7813 printk messages dropped ** [   30.400054] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 7666 printk messages dropped ** [   30.538391] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 7687 printk messages dropped ** [   30.676544] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 7960 printk messages dropped ** [   30.819915] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 8317 printk messages dropped ** [   30.966979] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 8590 printk messages dropped ** [   31.122528] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 8885 printk messages dropped ** [   31.287658] [<c0218ed0>] (fbcon_scroll) from [<c025af90>] (scrup+0x60/0x128)
> ** 9408 printk messages dropped ** [   31.461425] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 9787 printk messages dropped ** [   31.644287] [<c02187e8>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10081 printk messages dropped ** [   31.833984] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10501 printk messages dropped ** [   32.031066] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10816 printk messages dropped ** [   32.233001] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10900 printk messages dropped ** [   32.440490] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10837 printk messages dropped ** [   32.645233] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10837 printk messages dropped ** [   32.848999] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10837 printk messages dropped ** [   33.053833] [<c02187a4>] (fbcon_redraw.isra.12) from [<c0218ed0>] 
> (fbcon_scroll+0x6a0/0xcbc)
> ** 10838 printk messages dropped ** [   33.258361] [<c0218ed0>] (fbcon_scroll) from [<c025af90>] (scrup+0x60/0x128)
> 
> I suspect that problem is in omapdss.
> 
> I do not know if size 0 make sense, but Maemo userspace is calling above
> commands and on Nokia's 2.6.28 kernel there is no crash or error message.
> 
> IMHO Division by zero in kernel should not be there even if userspace
> call "incorrect" command.
> 

PING! Any idea what to do with Division by zero in kernel?

-- 
Pali Rohár
pali.rohar@...il.com
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