HI George,
Thanks, this information clears the situation. Now, question to you and David.
May we run into situation, when attacker dumps memory and analyses it for valuable content, instead of reserving it for own process, where it would be zeroed? My understanding, it is a possibility. Does kernel have any safeguard against it?
Thanks,
Oleg
On Wed, Dec 23, 2015 at 2:13 AM, George Neuner <gneuner2@xxxxxxxxxxx> wrote:
On Tue, 22 Dec 2015 23:21:27 +0000, David Wilson <dw+pg@xxxxxxxx>
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
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