On Tue, 22 Dec 2015 23:21:27 +0000, David Wilson <dw+pg@hmmz.org>
wrote:
>On Linux the memory pages of an exiting process aren't sanitized at
>exit, however it is impossible(?) for userspace to reallocate them
>without the kernel first zeroing their contents.
Not impossible, but it requires a non-standard kernel.
Since 2.6.33, mmap() accepts the flag MAP_UNINITIALIZED which allows
pages to be mapped without being cleared. The flag has no effect
unless the kernel was built with CONFIG_MMAP_ALLOW_UNINITIALIZED.
No mainstream distro enables this. AFAIK, there is NO distro at all
that enables it ... it's too big a security risk for a general purpose
system. It's intended to support embedded systems where the set of
programs is known.
George