linux-kernel - Re: [RFC PATCH v4 3/3] sysctl: return -EINVAL if val violates minmax

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Date:   Mon, 11 Feb 2019 11:50:25 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christian Brauner <christian@...uner.io>
Cc:     akpm@...ux-foundation.org, keescook@...omium.org,
        linux-kernel@...r.kernel.org, ebiederm@...ssion.com,
        joe.lawrence@...hat.com, longman@...hat.com,
        linux@...inikbrodowski.net, viro@...iv.linux.org.uk,
        adobriyan@...il.com, linux-api@...r.kernel.org
Subject: Re: [RFC PATCH v4 3/3] sysctl: return -EINVAL if val violates minmax

On Sun, Feb 10, 2019 at 09:39:43PM +0100, Christian Brauner wrote:
> Currently when userspace gives us a values that overflow e.g. file-max and
> other callers of __do_proc_doulongvec_minmax() we simply
> ignore the new value and leave the current value untouched. This can be
> problematic as it gives the illusion that the limit has indeed be bumped
> when in fact it failed.
> This commit makes sure to return EINVAL when an overflow is detected.
> Please note that this is a userspace facing change.
> 

Acked-by: Luis Chamberlain <mcgrof@...nel.org>

  Luis

> Signed-off-by: Christian Brauner <christian@...uner.io>
> ---
> /* Changelog */
> v4:
> - patch introduced
> 
> v1-v3:
> - patch not present
> ---
>  kernel/sysctl.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index c4a44b7ccb8a..516bc8a2812d 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2846,8 +2846,10 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
>  			if (neg)
>  				continue;
>  			val = convmul * val / convdiv;
> -			if ((min && val < *min) || (max && val > *max))
> -				continue;
> +			if ((min && val < *min) || (max && val > *max)) {
> +				err = -EINVAL;
> +				break;
> +			}
>  			*i = val;
>  		} else {
>  			val = convdiv * (*i) / convmul;
> -- 
> 2.20.1
>