On Tue, 7 Jun 2005, Peter Staubach wrote:
> Nagendra Singh Tomar wrote:
>
> >Hi all,
> > The short version first.
> >Is it OK for an application (a C library implementing malloc/calloc is
> >also an application) to assume that the pages returned by the OS for heap
> >allocation (either directly thru brk() or thru mmap(MAP_ANONYMOUS)) will
> >be zero filled.
> >
>
> An application which makes assumptions about the contents of newly allocated
> memory would seem to be making very dangerous assumptions.
Thats what glibc does. Ulrich confirmed that. I would say thats not a bad
optimization on glibc's part as it does not really make sense to zero out
a memory again in user space if we know for sure that new heap memory that
kernel hands over to us will be zeroed. I'm not sure though whether this
is a documented kernel ABI.
>
> Ignoring that, would it not be considered to be a security violation to hand
> pieces of memory to applications without erasing the old contents of the
> pages?
I understand that for a desktop/server running Linux but not for an
embedded box where all the applications that run on the box is controlled
by you.
Thanx,
Tomar
-- You have moved the mouse. Windows must be restarted for the
changes to take effect.
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