linux-kernel - Re: [PATCH] ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space

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Date:	Fri, 15 Jan 2010 17:30:44 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	hartleys@...ionengravers.com
Cc:	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	kuznet@....inr.ac.ru, pekkas@...core.fi, jmorris@...ei.org,
	yoshfuji@...ux-ipv6.org, kaber@...sh.net
Subject: Re: [PATCH] ipv4/ip_sockglue.c: copy msg_control optval from user
 to kernel space

From: H Hartley Sweeten <hartleys@...ionengravers.com>
Date: Fri, 15 Jan 2010 10:24:59 -0700

> ipv4/ip_sockglue.c: copy msg_control optval from user to kernel space
> 
> In do_ip_getsockopt the char __user *optval is used directly in
> IP_PKTOPTIONS for the msg.msg_control and not copied from
> user to kernel address space. This produces a sparse warning:
> 
> warning: incorrect type in assignment (different address spaces)
>    expected void *msg_control
>    got char [noderef] <asn:1>*optval
> 
> Fix this by using copy _from_user to set msg.msg_control.
> 
> Signed-off-by: H Hartley Sweeten <hsweeten@...ionengravers.com>

This isn't right.

We want the 'optval' pointer itself, not the data it points to, stored
in msg.msg_control

And 'msg_control' is, in this case a user pointer.

It just isn't annotated (along with the rest of struct msghdr) with
"__user" because we mix the usage of this object with kernel and user
pointers.

How did you test your change?
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