CVE request -- Linux kernel: mm: thp: pmd_present and PROT_NONE local DoS

[Petr Matousek <pmatouse () redhat com>]

Most VM places are using pmd_none but a few are still using pmd_present.
The meaning is about the same for the pmd. However pmd_present would
return the wrong value on PROT_NONE ranges. When the code using
pmd_present gets a false negative, the kernel will crash.

An unprivileged local user could use this flaw to crash the system.

Upstream fix:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=027ef6c8

References:
https://bugzilla.redhat.com/show_bug.cgi?id=912898

Thanks,
-- 
Petr Matousek / Red Hat Security Response Team