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

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Message-Id: <20151215.153626.1500179484827859040.davem@davemloft.net>
Date:	Tue, 15 Dec 2015 15:36:26 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	dvyukov@...gle.com
Cc:	lauro.venancio@...nbossa.org, aloisio.almeida@...nbossa.org,
	sameo@...ux.intel.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	syzkaller@...glegroups.com, edumazet@...gle.com, kcc@...gle.com,
	glider@...gle.com, sasha.levin@...cle.com
Subject: Re: Information leak in llcp_sock_bind/llcp_raw_sock_bind

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.

Even wrt. llcp_sock->service_name, the code limits the string to
NFC_LLCP_MAX_SERVICE_NAME.
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