Re: [patch -mm] mm, mempolicy: silence gcc warning

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 25 Nov 2013 19:08:15 -0500 KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:

> >>> It worries me that the CONFIG_NUMA=n version of mpol_to_str() doesn't
> >>> stick a '\0' into *buffer.  Hopefully it never gets called...
> >>
> >> Don't worry. It never happens. Currently, all of caller depend on CONFIG_NUMA.
> >> However it would be nice if CONFIG_NUMA=n version of mpol_to_str() is
> >> implemented
> >> more carefully. I don't know who's mistake.
> > 
> > Put a BUG() in there?
> 
> I think this is enough. What do you think?
> 
> 
> commit 5691f7f336c511d39fc05821d204a8f7ba18c0cf
> Author: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Date:   Mon Nov 25 18:38:25 2013 -0500
> 
>     mempolicy: implement mpol_to_str() fallback implementation when !CONFIG_NUMA
> 
>     Andrew Morton pointed out mpol_to_str() has no fallback implementation
>     for !CONFIG_NUMA and it could be dangerous because callers might assume
>     buffer is filled zero terminated string. Fortunately there is no such
>     caller. But it would be nice to provide default safe implementation.
> 
>     Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> 
> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
> index 9fe426b..eee0597 100644
> --- a/include/linux/mempolicy.h
> +++ b/include/linux/mempolicy.h
> @@ -309,6 +309,8 @@ static inline int mpol_parse_str(char *str, struct mempolicy **mpol)
> 
>  static inline void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
>  {
> +	strncpy(buffer, "default", maxlen-1);
> +	buffer[maxlen-1] = '\0';
>  }
> 

Well, as David said, BUILD_BUG() would be the preferred cleanup.  I'll
stick one in there and see what the build bot has to say?

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