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Subject: Re: [PATCH v2 2/2] UBI: Make mtd parameter readable
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Richard Weinberger <richard@nod.at>
Cc: Artem Bityutskiy <dedekind1@gmail.com>, Boris Brezillon
 <boris.brezillon@free-electrons.com>, "linux-mtd@lists.infradead.org"
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Date: Tue, 10 Jan 2017 16:11:36 +0200
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On Tue, 2017-01-10 at 14:54 +0100, Richard Weinberger wrote:
> Am 10.01.2017 um 14:48 schrieb Andy Shevchenko:
> > > > -module_param_call(mtd, ubi_mtd_param_parse, NULL, NULL, 000);
> > > > +module_param_call(mtd, ubi_mtd_param_parse, NULL, NULL, 0400);
> > > What is the use case?
> > > AFAIKT the permissions are 000
> > 
> > If it's not 0 in current case than you easily crash the kernel
> > because
> > parser will be gone at that time. This is fixed by patch 1.
> 
> Before your changes it was non-issue, right? ;)

If annoying section mismatch is not an issue, then yes, correct.

> > >  because a parser is involved and to
> > > "understand" the parameter,
> > > a reader needs the ubi_mtd_param_parse() function.
> > 
> > Are you implying that writer is a bot and reader is human being? 
> > The use case is obvious (any security reasons are implied?) -- allow
> > user to see what was written there in the first place.
> 
> I'm asking for the use case, why is exposing this parameter to user
> space
> a good thing? Who will use it?

Any user. I like the idea to have initial string to be stored somewhere
and visible (imagine the case when it's module and history is gone). It
might be useful for debugging (okay, this case perhaps not anymore, but
in general).

> > Permissions 0000 are error prone.
> 
> Why?

Because of a trick is being used here.

P.S. If you strongly against it I will give up, it doesn't cost my
efforts anymore. That's why one of the possible "solution" is to put
comment there for other brave guys.

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy