auditsc: audit_krule mask accesses need bounds checking

auditsc: audit_krule mask accesses need bounds checking

Fixes an easy DoS and possible information disclosure.

This does nothing about the broken state of x32 auditing.

eparis: If the admin has enabled auditd and has specifically loaded
audit rules.  This bug has been around since before git.  Wow...

Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Origin: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=a3c54931199565930d6d84f4c3456f6440aefd41
Backported-by: Maciej Wereski <m.wereski@partner.samsung.com>
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>
Change-Id: Ic36da623453b4507d93be2c68f8be6945da2df6c