x86/mce: Avoid using object after free in genpool

x86/mce: Avoid using object after free in genpool

When we loop over all queued machine check error records to pass them
to the registered notifiers we use llist_for_each_entry(). But the loop
calls gen_pool_free() for the entry in the body of the loop - and then
the iterator looks at node->next after the free.

Use llist_for_each_entry_safe() instead.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Cc: Gong Chen <gong.chen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/0205920@agluck-desk.sc.intel.com
Link: http://lkml.kernel.org/r/1459929916-12852-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>