linux-kernel - Re: [patch] vga_switcheroo: comparing too few characters in strncmp()

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Message-ID: <20110107053054.GA9057@p183.telecom.by>
Date:	Fri, 7 Jan 2011 07:30:54 +0200
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Dan Carpenter <error27@...il.com>,
	Dave Airlie <airlied@...hat.com>, Jiri Slaby <jslaby@...e.cz>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [patch] vga_switcheroo: comparing too few characters in
 strncmp()

On Fri, Jan 07, 2011 at 08:12:27AM +0300, Dan Carpenter wrote:
> This is a copy-and-paste bug.  We should be comparing 4 characters here
> instead of 3.

> --- a/drivers/gpu/vga/vga_switcheroo.c
> +++ b/drivers/gpu/vga/vga_switcheroo.c
> @@ -346,11 +346,11 @@ vga_switcheroo_debugfs_write(struct file *filp, const char __user *ubuf,
>  	if (strncmp(usercmd, "DIS", 3) == 0)
>  		client_id = VGA_SWITCHEROO_DIS;
>  
> -	if (strncmp(usercmd, "MIGD", 3) == 0) {
> +	if (strncmp(usercmd, "MIGD", 4) == 0) {
>  		just_mux = true;
>  		client_id = VGA_SWITCHEROO_IGD;
>  	}
> -	if (strncmp(usercmd, "MDIS", 3) == 0) {
> +	if (strncmp(usercmd, "MDIS", 4) == 0) {

How about you NUL-terminate, and use strcmp().
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