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

Started byJérémy Lefaure <jeremy.lefaure@lse.epita.fr>
First post2017-04-19 22:40 +0200
Last post2017-04-22 01:10 +0200
Articles 3 — 3 participants

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  [PATCH] FS-Cache: print hexadecimal value for special cookies type Jérémy Lefaure          <jeremy.lefaure@lse.epita.fr> - 2017-04-19 22:40 +0200
    Re: [PATCH] FS-Cache: print hexadecimal value for special cookies type Andy Shevchenko <andy.shevchenko@gmail.com> - 2017-04-21 21:50 +0200
      Re: [PATCH] FS-Cache: print hexadecimal value for special cookies  type Jérémy Lefaure <jeremy.lefaure@lse.epita.fr> - 2017-04-22 01:10 +0200

#1626778 — [PATCH] FS-Cache: print hexadecimal value for special cookies type

FromJérémy Lefaure <jeremy.lefaure@lse.epita.fr>
Date2017-04-19 22:40 +0200
Subject[PATCH] FS-Cache: print hexadecimal value for special cookies type
Message-ID<ty4yl-7Xj-5@gated-at.bofh.it>
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.

Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
---
 fs/fscache/object-list.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
index 67f940892ef8..d51303124889 100644
--- a/fs/fscache/object-list.c
+++ b/fs/fscache/object-list.c
@@ -262,7 +262,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
 			type = "DT";
 			break;
 		default:
-			sprintf(_type, "%02u", cookie->def->type);
+			sprintf(_type, "%02x", cookie->def->type);
 			type = _type;
 			break;
 		}
-- 
2.12.2

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#1628555

FromAndy Shevchenko <andy.shevchenko@gmail.com>
Date2017-04-21 21:50 +0200
Message-ID<tyMJ3-1nm-1@gated-at.bofh.it>
In reply to#1626778
On Wed, Apr 19, 2017 at 11:38 PM, Jérémy Lefaure
<jeremy.lefaure@lse.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.

If this is used by some user space tool the safest fix is to print in
BCD and fix documentation.

> Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
> ---
>  fs/fscache/object-list.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
> index 67f940892ef8..d51303124889 100644
> --- a/fs/fscache/object-list.c
> +++ b/fs/fscache/object-list.c
> @@ -262,7 +262,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
>                         type = "DT";
>                         break;
>                 default:
> -                       sprintf(_type, "%02u", cookie->def->type);
> +                       sprintf(_type, "%02x", cookie->def->type);
>                         type = _type;
>                         break;
>                 }
> --
> 2.12.2
>



-- 
With Best Regards,
Andy Shevchenko

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#1628664 — Re: [PATCH] FS-Cache: print hexadecimal value for special cookies type

FromJérémy Lefaure <jeremy.lefaure@lse.epita.fr>
Date2017-04-22 01:10 +0200
SubjectRe: [PATCH] FS-Cache: print hexadecimal value for special cookies type
Message-ID<tyPQB-3tW-3@gated-at.bofh.it>
In reply to#1628555
On Fri, 21 Apr 2017 22:41:54 +0300
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Wed, Apr 19, 2017 at 11:38 PM, Jérémy Lefaure
> <jeremy.lefaure@lse.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.  
> 
> If this is used by some user space tool the safest fix is to print in
> BCD and fix documentation.
> 
Are you talking about the Binary Coded Decimal format ? I don't get why
it would be better. If we change the printed format, it would break
user space tool anyway, right ?

> > Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
> > ---
> >  fs/fscache/object-list.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/fs/fscache/object-list.c b/fs/fscache/object-list.c
> > index 67f940892ef8..d51303124889 100644
> > --- a/fs/fscache/object-list.c
> > +++ b/fs/fscache/object-list.c
> > @@ -262,7 +262,7 @@ static int fscache_objlist_show(struct seq_file *m, void *v)
> >                         type = "DT";
> >                         break;
> >                 default:
> > -                       sprintf(_type, "%02u", cookie->def->type);
> > +                       sprintf(_type, "%02x", cookie->def->type);
> >                         type = _type;
> >                         break;
> >                 }
> > --
> > 2.12.2
> >  
> 
> 
>

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