Re: quick malloc guard patch

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02-22-2008, 11:34 AM

Jonathan Thornburg

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Re: quick malloc guard patch

In http://marc.theaimsgroup.com/?l=open...0463414314&w=1,
Tad Unangst wrote
> when malloc gets a request with a size equal to the size of a pointer, we
> can allocate a whole page, and return a pointer 4 bytes from the end. the
> four bytes allocated are useable, but don't touch the fifth or any later
> ones. (8 bytes on 64bit archs).
>
> when running with this patch and malloc guard, any attempt to access
> fields of foo after the first will cause the program containing the above
> code to crash. typically just after the problem allocation. having
> seen and fixed several bugs of this nature, i can say that they're
> fairly prevalent. happy hunting.
>
> [[patch snipped]]

Is the plan to make this the default behavior, or "just" to add it as
another option selectable by /etc/malloc.conf?

ciao,

--
-- "Jonathan Thornburg (remove -animal to reply)" <jthorn@aei.mpg-zebra.de>
Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
Golm, Germany, "Old Europe" http://www.aei.mpg.de/~jthorn/home.html
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam

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Re: quick malloc guard patch