linux-kernel - Re: [PATCH RFC 1/2] PM / Hibernate: use name_to_dev

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Message-ID: <20130918130100.GB2467@amd.pavel.ucw.cz>
Date:	Wed, 18 Sep 2013 15:01:00 +0200
From:	Pavel Machek <pavel@....cz>
To:	Sebastian Capella <sebastian.capella@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-pm@...r.kernel.org, linaro-dev@...ts.linaro.org,
	len.brown@...el.com
Subject: Re: [PATCH RFC 1/2] PM / Hibernate: use name_to_dev_t to parse
 resume

On Tue 2013-09-17 13:50:21, Sebastian Capella wrote:
> Quoting Sebastian Capella (2013-08-30 11:42:30)
> > Quoting Pavel Machek (2013-08-30 04:35:33)
> > > On Mon 2013-08-26 10:40:50, Sebastian Capella wrote:
> > > > Quoting Pavel Machek (2013-08-25 08:38:11)
> > > > > Is the allocation actually neccessary? At the very least this should
> > > > > test for NULL...
> > > > 
> > > > name_to_dev_t expects a non-const name, but the buffer passed in
> > > > is const.  I also am removing the '\n' if found at the end of the
> > > > string which would violate the const.
> > > 
> > > Fix name_to_dev_t, then. No need to do memory allocation just to work
> > > around const.
> > > 
> > Hi Pavel,
> > 
> > The issue is really Removing the \n from the user space input.  The
> > flow is:
> > const input buf -> copy to work buffer, remove newline -> name_to_dev_t
> > 
> >   ssize_t resume_store(..., const char *buf, size_t n)
> >   // copy buf, strip off trailing newline, pass to name_to_dev_t
> >   dev_t name_to_dev_t(char *name)
> > 
> > The const in the restore_store buffer comes from the function type of the
> > store member of the kobj_attribute.  I don't believe this should be changed.
> > 
> > Currently, name_to_dev_t will fail in some cases if a trailing \n is present.
> > Is it more appropriate to handle stripping the newline in the store
> > function rather than modifying name_to_dev_t to clean it up?
> > 
> > It seems logical for name_to_dev_t to take a const name parameter as
> > there should be no reason to modify the name buffer passed to it.
> > I'll be happy to make a patch to do this, but without hardening
> > name_to_dev_t against trailing newlines, it would not be neccesary for
> > this problem.
> > 
> > Thanks for your time and comments!
> > 
> 
> Hi Pavel,
> 
> Do you have any more feedback regarding leaving the strndup?

I think you should modify name_to_dev_t, then. Doing memory allocation
just to work around \n limitation is ugly.
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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