[PATCH v4 3/3] xen-blkfront: transverse list of persistent grants safely

[Roger Pau Monne <roger.pau@citrix.com>]

Use llist_for_each_entry_safe in blkif_free. Previously grants where
freed while iterating the list, which lead to dereferences when trying
to fetch the next item.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: xen-devel@lists.xen.org
---
 drivers/block/xen-blkfront.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 96e9b00..8ae8062 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -791,7 +791,7 @@ static void blkif_restart_queue(struct work_struct *work)
 static void blkif_free(struct blkfront_info *info, int suspend)
 {
 	struct llist_node *all_gnts;
-	struct grant *persistent_gnt;
+	struct grant *persistent_gnt, *n;
 
 	/* Prevent new requests being issued until we fix things up. */
 	spin_lock_irq(&info->io_lock);
@@ -804,7 +804,7 @@ static void blkif_free(struct blkfront_info *info, int suspend)
 	/* Remove all persistent grants */
 	if (info->persistent_gnts_c) {
 		all_gnts = llist_del_all(&info->persistent_gnts);
-		llist_for_each_entry(persistent_gnt, all_gnts, node) {
+		llist_for_each_entry_safe(persistent_gnt, n, all_gnts, node) {
 			gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
 			__free_page(pfn_to_page(persistent_gnt->pfn));
 			kfree(persistent_gnt);
-- 
1.7.7.5 (Apple Git-26)