Subject: Re: [PATCH 1/3] netfilter: Fix copy_to_user too small size parametre.

From: Pablo Neira Ayuso <[email-masked]>
Date: Thu, 1 Mar 2012 14:03:11 +0100

On Thu, Mar 01, 2012 at 04:15:05PM +0530, santosh prasad nayak wrote:
> Hi Pablo.
> 
> copy_to_user( dest, source, length)
> 
> Normally,  'length'  is equal to  'sizeof (source) '.
> 
> In this case "length"   =   32
>        "sizeof(source)"  =   29.
> 
> Is it intentional ?

ebtables expects 32 bytes names.

> Won't it copy extra 3 bytes of kernel data to userspace ?

You're right. We have to copy 29 bytes but we have to fill the
remaining bytes with zeroes. I think something like:

char name[EBT_FUNCTION_MAXNAMELEN] = {};

/* user-space ebtables expects 32 bytes-long names, but xt_match uses
 * 29 bytes for that. */
sprintf(name, "%s", m->u.match->name);
if (copy_to_user(hlp, name, EBT_FUNCTION_MAXNAMELEN))
...

will resolve this issue.

Would you resend a new patch?