Re: [PATCH v2 1/1] drm: modes: fix DRM modes analysis regression

[Daniel Vetter]

On Wed, Dec 09, 2015 at 08:11:39PM +0100, Corentin LABBE wrote:
> Le 09/12/2015 16:32, Jani Nikula a écrit :
> > On Wed, 09 Dec 2015, LABBE Corentin <clabbe.montjoie@xxxxxxxxx> wrote:
> >> My latest commit introduce some case where a valid mode, could be
> >> rejected.
> >> simple_strtox functions stop at first non-digit character, but kstrtox not.
> >> So args like "video=HDMI-A-1:720x480-16@60" will be reject when checking 16@.
> >> The proper solution is to store digits in a specific buffer.
> > 
> > Or to revert regressing commit...? Your original commit complicated the
> > already complicated function, and this one makes it more so. What is the
> > benefit?
> > 
> 
> The benefit is to remove a function marked obsolete who do not said if the conversation is successful or not.
> But I understand that the way I have done it was not the best one.
> If the maintainer want it, I will send a patch for reverting the first patch.

Given that nothin bad happens if we misparse the number (black screen) and
there's no screen resolution even close to the limit of what can be
parsed, I think reverting is the right action.

Carefully parsing userspace input makes sense. But this is the kernel
cmdline, if your attacker can change that you've lost no matter what.

Please send in the revert with a short summary of the discussion here.

Thanks, Daniel

> 
> >> Fixes: 52157a4ca396 ("drm: modes: replace simple_strtoul by kstrtouint")
> > 
> > For me the commit id is cc344980c76748e57c9c03100c2a14d36ab00334.
> 
> Oups, I took commit id from my local git.
> 
> Regards
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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