linux-kernel - Re: [PATCH v2 net-next] fix unsafe set_memory

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Date:	Thu, 03 Oct 2013 16:07:46 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexei Starovoitov <ast@...mgrid.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Xi Wang <xi.wang@...il.com>, x86@...nel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next] fix unsafe set_memory_rw from softirq

On Thu, 2013-10-03 at 15:47 -0700, Alexei Starovoitov wrote:

> @@ -722,7 +725,8 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy);
>  int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
>  {
>  	struct sk_filter *fp, *old_fp;
> -	unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
> +	unsigned int fsize = max(sizeof(struct sock_filter) * fprog->len,
> +				 sizeof(struct work_struct));
>  	int err;
>  
>  	if (sock_flag(sk, SOCK_FILTER_LOCKED))

Thats broken, as we might copy more data from user than expected,
and eventually trigger EFAULT :

if (copy_from_user(fp->insns, fprog->filter, fsize)) {


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