linux-kernel - RE: [PATCH] efi: fix out-of-bounds null overwrite vulnerability

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F39FA7208@ORSMSX114.amr.corp.intel.com>
Date:	Fri, 8 Jan 2016 16:47:17 +0000
From:	"Luck, Tony" <tony.luck@...el.com>
To:	Matt Fleming <matt@...eblueprint.co.uk>,
	Insu Yun <wuninsu@...il.com>
CC:	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"taesoo@...ech.edu" <taesoo@...ech.edu>,
	"yeongjin.jang@...ech.edu" <yeongjin.jang@...ech.edu>,
	"insu@...ech.edu" <insu@...ech.edu>,
	"changwoo@...ech.edu" <changwoo@...ech.edu>
Subject: RE: [PATCH] efi: fix out-of-bounds null overwrite vulnerability

> But this function doesn't use snprintf(), it uses scnprintf() which
> returns the number of characters written into buf and, because
> scnprintf() largely follows vnsprintf(), it will never write more than
> 'size' bytes into the buffer.

        if (bank && device)
                n = snprintf(msg, len, "DIMM location: %s %s ", bank, device);

That looks like "snprintf", not "scnprintf" to me :-)

What about using:

	msg[len] = '\0';

to guarantee NUL termination?

-Tony