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Re: malloc_set_state and heap content


On 07/06/2016 10:38 PM, Samuel Thibault wrote:
Florian Weimer, on Wed 06 Jul 2016 22:36:05 +0200, wrote:
On 07/06/2016 09:35 PM, Samuel Thibault wrote:
On Linux the space happens to be zero by luck, but with other kernels
that may not be true (it is not with the Hurd).

How gets Hurd away with that without introducing a security vulnerability?

What remains on the heap is initialization stuff, not remainders from
pages allocated by the kernel.

I still don't see how this is correct. Maybe the Hurd startup code mallocs so much that it consumes all that data before the application can call calloc. Otherwise, an early calloc call would return non-zero memory.

So I'd say we need the attached patch, don't we?

The patch does not address the issue because it does not alter the heap copy
in existing Emacs binaries.  It would only become effective after
recompiling Emacs.  Such recompiled Emacs binaries will no longer use the
heap dumping mechanism.

Well, glibc is not only about emacs, is it? :)

Could you be more specific, please? Are there Hurd-specific applications which use malloc_set_state?

Thanks,
Florian


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