linux-kernel - Re: [PATCH] sysctl: remove impossible condition check

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Date:	Wed, 1 Jun 2011 11:11:36 -0300
From:	Lucas De Marchi <lucas.demarchi@...fusion.mobi>
To:	Jesper Juhl <jj@...osbits.net>
Cc:	linux-kernel@...r.kernel.org, Nick Piggin <npiggin@...nel.dk>,
	Christoph Hellwig <hch@....de>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH] sysctl: remove impossible condition check

[ CC'ing Al Viro ]

On Wed, Jun 1, 2011 at 10:25 AM, Jesper Juhl <jj@...osbits.net> wrote:
> How about compacting it even further by getting rid of the 'len' variable
> as well?
> Like this:
>
> Signed-off-by: Jesper Juhl <jj@...osbits.net>
> ---
>  proc_sysctl.c |   10 ++--------
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index f50133c..bd7f7af 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -49,17 +49,11 @@ out:
>
>  static struct ctl_table *find_in_table(struct ctl_table *p, struct qstr *name)
>  {
> -       int len;
>        for ( ; p->procname; p++) {
> -
> -               if (!p->procname)
> -                       continue;
> -
> -               len = strlen(p->procname);
> -               if (len != name->len)
> +               if (strlen(p->procname) != name->len)
>                        continue;
>
> -               if (memcmp(p->procname, name->name, len) != 0)
> +               if (memcmp(p->procname, name->name, name->len) != 0)
>                        continue;
>
>                /* I have a match */
>


Looking again at the code, I'm wondering if this is not actually a
bug. There might be entries with procname == NULL, meaning they are
not mirrored in /proc. What seems wrong is the condition in the for().
It should stop when all fields are 0 (meaning the end of the table)
instead of stopping when procname is NULL.

>
> --
> Jesper Juhl <jj@...osbits.net>       http://www.chaosbits.net/
> Don't top-post http://www.catb.org/jargon/html/T/top-post.html
> Plain text mails only, please.
>
>
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