[PATCH] drm/tinydrm: fix a loop in debugfs code

[Noralf Trønnes]

Den 21.08.2019 09.24, skrev Dan Carpenter:
> This code will likely crash if we try to do a zero byte write.  The code
> looks like this:
> 
>         /* strip trailing whitespace */
>         for (i = count - 1; i > 0; i--)
>                 if (isspace(buf[i]))
> 			...
> 
> We're writing zero bytes so count = 0.  You would think that "count - 1"
> would be negative one, but because "i" is unsigned it is a large
> positive numer instead.  The "i > 0" condition is true and the "buf[i]"
> access will be out of bounds.
> 
> The fix is to make "i" signed and now everything works as expected.  The
> upper bound of "count" is capped in __kernel_write() at MAX_RW_COUNT so
> we don't have to worry about it being higher than INT_MAX.
> 
> Fixes: 02dd95fe3169 ("drm/tinydrm: Add MIPI DBI support")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>
> ---

Thanks Dan, applied to drm-misc-next with adjusted title:
-drm/tinydrm: fix a loop in debugfs code
+drm/mipi-dbi: fix a loop in debugfs code

Noralf.