linux-kernel - Re: [PATCH v2] firmware: make sure paths remain relative

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Message-ID: <20121218220223.5ae69bf0@pyramind.ukuu.org.uk>
Date:	Tue, 18 Dec 2012 22:02:23 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org, Ming Lei <ming.lei@...onical.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2] firmware: make sure paths remain relative

On Tue, 18 Dec 2012 13:04:49 -0800
Kees Cook <keescook@...omium.org> wrote:

> Some devices have configurable firmware locations. If these configuration
> mechanisms are exposed to unprivileged userspace, it may be possible to
> load firmware from an unexpected location. To minimize the risk of this,
> make sure the string "../" does not appear in the firmware name. This
> means that neither the users of request_firmware, nor the uevent handler
> have to do this filtering themselves.

Have you verified no existing distribution ever does this ?


> +	if (strstr(name, "../")) {

and this is obviously buggy and hasn't been tested

Hint foo/bar../baz

You need to check for ^../ /../ and /..$

Alan
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