netdev - Re: [PATCH] sock filter: fix copy of filter from userspace

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Date:	Sat, 13 Oct 2012 21:19:49 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	Jiri Pirko <jpirko@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] sock filter: fix copy of filter from userspace

Sat, Oct 13, 2012 at 08:40:32PM CEST, shemminger@...tta.com wrote:
>The sk_unattached_filter_create function is passed a socket
>filter structure and the copies the contents of the filter from
>userspace. Sparse detected that this code was incorrectly using
>memcpy when it needed to use copy_from_user instead.

Hmm. fprog->filter is in this case allocated and filled in kernel.
So memcpy is good.

Not sure how to handle this correctly. Either we remove "__user" or we
redefine "struct sock_fprog" for sk_unattached_filter_create() use.

Any thoughts?

>
>The only use of sk_unattached_filter_create at present is in
>the team driver.
>
>Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>
>
>--- a/net/core/filter.c	2012-10-09 10:35:03.183141638 -0700
>+++ b/net/core/filter.c	2012-10-13 11:33:05.955531440 -0700
>@@ -666,7 +666,9 @@ int sk_unattached_filter_create(struct s
> 	fp = kmalloc(fsize + sizeof(*fp), GFP_KERNEL);
> 	if (!fp)
> 		return -ENOMEM;
>-	memcpy(fp->insns, fprog->filter, fsize);
>+
>+	if (copy_from_user(fp->insns, fprog->filter, fsize))
>+		return -EFAULT;
> 
> 	atomic_set(&fp->refcnt, 1);
> 	fp->len = fprog->len;
>--
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