linux-kernel - Re: [PATCH] FS-Cache: print hexadecimal value for special cookies type

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Date:   Thu, 27 Apr 2017 11:11:29 -0400
From:   Jérémy Lefaure <jeremy.lefaure@....epita.fr>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-cachefs@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] FS-Cache: print hexadecimal value for special cookies
 type

On Thu, 27 Apr 2017 16:03:45 +0100
David Howells <dhowells@...hat.com> wrote:

> Jérémy Lefaure <jeremy.lefaure@....epita.fr> wrote:
> 
> > When building object-list.o, gcc 6 raises a warning on the sprintf call
> > in fscache_objlist_show:
> > 
> >   CC      fs/fscache/object-list.o
> > fs/fscache/object-list.c: In function ‘fscache_objlist_show’:
> > fs/fscache/object-list.c:265:19: warning: ‘sprintf’ may write a
> > terminating nul past the end of the destination [-Wformat-overflow=]
> >     sprintf(_type, "%02u", cookie->def->type);
> >                    ^~~~~~
> > fs/fscache/object-list.c:265:4: note: ‘sprintf’ output between 3 and 4
> > bytes into a destination of size 3
> >     sprintf(_type, "%02u", cookie->def->type);
> >     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 
> > Moreover, the documentation says that we should have an hex value for
> > special cookies (see Documentation/filesystems/caching/fscache.txt).
> > 
> > Printing hexadecimal value for special cookies fixes the overflow
> > warning and complies with the documentation.  
> 
> Fine by me.  We don't actually handle special type cookies at the moment, so
> you're not going to see anything other than DT or IX for now anyway.
> 
> I'll push this in the next merge window if that's okay with you.
> 
Did you see the v2 of my patch (in which I keep the decimal value but
fix the buffer size) ? If special type cookies aren't handled, I guess
that this v1 is better, isn't it ?