[PATCH] x86/mce: Avoid using object after free in genpool.

[Tony Luck]

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.

Cc: sta...@vger.kernel.org
Signed-off-by: Tony Luck <tony.l...@intel.com>
---
 arch/x86/kernel/cpu/mcheck/mce-genpool.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce-genpool.c 
b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
index 0a850100c594..2658e2af74ec 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-genpool.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-genpool.c
@@ -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));
-- 
2.5.0