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Re: [patch] Fix for heap overflow in wscanf (BZ 16618)
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: Rich Felker <dalias at libc dot org>, Paul Eggert <eggert at cs dot ucla dot edu>
- Cc: Paul Pluzhnikov <ppluzhnikov at google dot com>, Andreas Schwab <schwab at suse dot de>, libc-alpha at sourceware dot org
- Date: Tue, 03 Feb 2015 23:33:33 -0500
- Subject: Re: [patch] Fix for heap overflow in wscanf (BZ 16618)
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On 02/03/2015 07:27 PM, Rich Felker wrote:
> On Tue, Feb 03, 2015 at 04:11:56PM -0800, Paul Eggert wrote:
>> Carlos O'Donell wrote:
>>> I'd read the POSIX wording differently.
>> Although Rich's interpretation is correct for current POSIX, thanks
>> to Eric Blake the next release of POSIX (Issue 8) is planned to
>> change this, and to require 'free' to leave errno alone, which as I
>> understand it is your preferred interpretation. Please see:
>> Because of this, glibc 'free' should not set errno if the user
>> invokes 'free' in a conforming way. Setting errno will be a
>> conformance bug once Issue 8 comes out, and glibc should be fixed to
>> conform well before that. Also, the glibc documentation should be
>> changed to discuss this issue. I have filed a glibc bug report to
>> that effect, here:
> Interesting. Unfortunately this makes it impossible for the
> application to observe the "valid memory was unable to be freed"
> condition that occurs when you can't split a vma. Formally, the memory
> is still freed anyway, so it hardly matters, but it indicates a
> critical situation where things are about to blow up for the
> application (malloc no longer working, etc.) so conceivably an
> application could want to detect and respond to the condition.
Could you expand a bit on the split vma issue? I'm not familiar
with that failure mode.