linux-kernel - Re: [PATCH v3] proc_sysctl: fix oops caused by incorrect command parameters.

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Date:   Mon, 11 Jan 2021 20:33:40 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Xiaoming Ni <nixiaoming@...wei.com>
Cc:     <linux-kernel@...r.kernel.org>, <mcgrof@...nel.org>,
        <keescook@...omium.org>, <yzaikin@...gle.com>,
        <adobriyan@...il.com>, <linux-fsdevel@...r.kernel.org>,
        <vbabka@...e.cz>, <mhocko@...e.com>, <andy.shevchenko@...il.com>,
        <wangle6@...wei.com>
Subject: Re: [PATCH v3] proc_sysctl: fix oops caused by incorrect command
 parameters.

On Tue, 12 Jan 2021 11:31:55 +0800 Xiaoming Ni <nixiaoming@...wei.com> wrote:

> The process_sysctl_arg() does not check whether val is empty before
>  invoking strlen(val). If the command line parameter () is incorrectly
>  configured and val is empty, oops is triggered.
> 
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -1770,6 +1770,9 @@ static int process_sysctl_arg(char *param, char *val,
>  			return 0;
>  	}
>  
> +	if (!val)
> +		return -EINVAL;
> +

I think v2 (return 0) was preferable.  Because all the other error-out
cases in process_sysctl_arg() also do a `return 0'.

If we're going to do a separate "patch: make process_sysctl_arg()
return an errno instead of 0" then fine, we can discuss that.  But it's
conceptually a different work from fixing this situation.