Re: [PATCH] sysctl: Check length at deprecated_sysctl_warning.

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

On Tue, 13 Nov 2007 12:07:23 +0900 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:

> Andrew, please replace previous patch with this one.
> This one returns -ENOTDIR.
> ----------
> 
> Original patch forgot to check args->nlen.
> I don't know why args->nlen == CTL_MAXNAME is rejected,
> but it has been rejected traditionally.
> 
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  kernel/sysctl.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff -puN kernel/sysctl.c~sysctl-check-length-at-deprecated_sysctl_warning kernel/sysctl.c
> --- a/kernel/sysctl.c~sysctl-check-length-at-deprecated_sysctl_warning
> +++ a/kernel/sysctl.c
> @@ -2609,6 +2609,10 @@ static int deprecated_sysctl_warning(str
>  	int name[CTL_MAXNAME];
>  	int i;
>  
> +	/* Check args->nlen. */
> +	if (args->nlen <= 0 || args->nlen >= CTL_MAXNAME)

I believe (args->nlen > CTL_MAXNAME) was correct.

> +		return -ENOTDIR;

Ho hum.  Why does that code return -ENOTDIR on error anyway?

> +
>  	/* Read in the sysctl name for better debug message logging */
>  	for (i = 0; i < args->nlen; i++)
>  		if (get_user(name[i], args->name + i))