Patch "x86/mce: Avoid using object after free in genpool" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/mce: Avoid using object after free in genpool

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-mce-avoid-using-object-after-free-in-genpool.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Tony Luck <[email protected]>
Date: Wed, 6 Apr 2016 10:05:16 +0200
Subject: x86/mce: Avoid using object after free in genpool

From: Tony Luck <[email protected]>

commit a3125494cff084b098c80bb36fbe2061ffed9d52 upstream.

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.

---
 arch/x86/kernel/cpu/mcheck/mce-genpool.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -29,7 +29,7 @@ static char gen_pool_buf[MCE_POOLSZ];
 void mce_gen_pool_process(void)
 {
 	struct llist_node *head;
-	struct mce_evt_llist *node;
+	struct mce_evt_llist *node, *tmp;
 	struct mce *mce;
 
 	head = llist_del_all(&mce_event_llist);

@@ -37,7 +37,7 @@ void mce_gen_pool_process(void)
 		return;
 
 	head = llist_reverse_order(head);
-	llist_for_each_entry(node, head, llnode) {
+	llist_for_each_entry_safe(node, tmp, head, llnode) {
 		mce = &node->mce;
 		atomic_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
 		gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-mce-avoid-using-object-after-free-in-genpool.patch