linux-kernel - Re: Information leak in llcp_sock_bind/llcp_raw_sock

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Date:	Tue, 15 Dec 2015 21:45:16 +0100
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	syzkaller <syzkaller@...glegroups.com>
Cc:	Lauro Ramos Venancio <lauro.venancio@...nbossa.org>,
	Aloisio Almeida Jr <aloisio.almeida@...nbossa.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	linux-wireless@...r.kernel.org, netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Kostya Serebryany <kcc@...gle.com>,
	Alexander Potapenko <glider@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>
Subject: Re: Information leak in llcp_sock_bind/llcp_raw_sock_bind

On Tue, Dec 15, 2015 at 9:36 PM, David Miller <davem@...emloft.net> wrote:
> From: Dmitry Vyukov <dvyukov@...gle.com>
> Date: Tue, 15 Dec 2015 21:00:20 +0100
>
>> The problem is that llcp_sock_bind/llcp_raw_sock_bind do not check
>> sockaddr_len passed in, so they copy stack garbage from stack into the
>> socket and then return it in getsockname.
>> This can defeat ASLR, leak crypto keys, etc.
>
> That's actually the first thing these functions do.
>
> They completely clear out the on-stack llcp_addr, then they copy only
> as much as the user gave them, being careful not to use more than
> sizeof(llcp_addr).
>
>         memset(&llcp_addr, 0, sizeof(llcp_addr));
>         len = min_t(unsigned int, sizeof(llcp_addr), alen);
>         memcpy(&llcp_addr, addr, len);
>
> I don't see what the problem is, you'll need to be more specific.

You are right. Sorry.

There still seems to be a minor leak here:

  if (!addr || addr->sa_family != AF_NFC)
      return -EINVAL;

addr->sa_family can be uninit.
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