Messages in this thread | | | Date | Tue, 28 Jan 2014 12:51:08 -0800 | Subject | Re: [PATCH] vsprintf: ignore arguments to %n | From | Kees Cook <> |
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On Mon, Jan 27, 2014 at 5:02 PM, Ryan Mallon <rmallon@gmail.com> wrote: > On 28/01/14 11:39, Kees Cook wrote: >> If arguments are consumed without output when encountering %n, it >> could be used to benefit or improve information leak attacks that were >> exposed via a limited size buffer. Since %n is not used by the kernel, >> there is no reason to make an info leak attack any easier. > > I was thinking more like the following. Print the warning if %n is > detected in format_decode(), but otherwise just remove the handling of > %n outright and treat it like any other invalid format specifier. > Something like this completely untested patch. Thoughts?
I'd be totally fine with it. Minor typo in the comment before the WARN_ONCE (should be "its" instead of "it"), but otherwise looks good. Consider it:
Acked-by: Kees Cook <keescook@chromium.org>
It builds and boots fine for me, FWIW.
-Kees
-- Kees Cook Chrome OS Security
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