linux-kernel - RE: Resend [PATCH] netfilter: Fix copy_to

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Date:	Fri, 2 Mar 2012 09:05:10 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"santosh nayak" <santoshprasadnayak@...il.com>,
	<bart.de.schuymer@...dora.be>
Cc:	<pablo@...filter.org>, <kaber@...sh.net>, <shemminger@...tta.com>,
	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	<netfilter-devel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel-janitors@...r.kernel.org>
Subject: RE: Resend [PATCH] netfilter: Fix copy_to_user too small size parametre.

 
> -	if (copy_to_user(hlp, m->u.match->name, 
> EBT_FUNCTION_MAXNAMELEN))
> +	char name[EBT_FUNCTION_MAXNAMELEN] = {};
> +
> +	strncpy(name, m->u.match->name, sizeof(name));
> +	if (copy_to_user(hlp, name, EBT_FUNCTION_MAXNAMELEN))
>  		return -EFAULT;

strncpy() is very rarely the function you are looking for.
In this case it MIGHT be right (since you do a fixed size
copy_to_user).
OTOH there is no need to also initialise name[].
And it isn't entirely clear whether the application
is allowed to be given a non-terminated string.

	David


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