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Re: [patch] Fix for heap overflow in wscanf (BZ 16618)
- From: Florian Weimer <fweimer at redhat dot com>
- To: "Carlos O'Donell" <carlos at redhat dot com>, Paul Pluzhnikov <ppluzhnikov at google dot com>
- Cc: Paul Eggert <eggert at cs dot ucla dot edu>, Andreas Schwab <schwab at suse dot de>, Rich Felker <dalias at libc dot org>, GLIBC Devel <libc-alpha at sourceware dot org>
- Date: Fri, 06 Feb 2015 16:34:21 +0100
- Subject: Re: [patch] Fix for heap overflow in wscanf (BZ 16618)
- Authentication-results: sourceware.org; auth=none
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On 02/06/2015 04:29 PM, Carlos O'Donell wrote:
> On 02/06/2015 10:19 AM, Paul Pluzhnikov wrote:
>> On Fri, Feb 6, 2015 at 6:45 AM, Carlos O'Donell <firstname.lastname@example.org> wrote:
>>> On 02/06/2015 08:45 AM, Florian Weimer wrote:
>>>> I think this fixes as CVE-2015-1473 as well,
> Could you expand a bit on this comment? Did you test that it fixes the issue?
> Did you review that it's actually the same bug?
> I trust your review, but "Correct." is not sufficiently verbose for me and
> I want to make sure we're all in agreement.
The old code had this:
size_t newsize = (UCHAR_MAX + 1 > 2 * wpmax \
? UCHAR_MAX + 1 : 2 * wpmax); \
if (use_malloc || !__libc_use_alloca (newsize)) \
wp = (CHAR_T *) extend_alloca (wp, s, \
newsize * sizeof (CHAR_T)); \
Which is to say, the alloca policy check was against newsize, but the
actual allocation used newsize * sizeof (CHAR_T).
The new version computes newsize in bytes and uses it consistently,
addressing this discrepancy.
Florian Weimer / Red Hat Product Security