From ebb351cf78ee6bf3262e6b4b6906f456c05e6d5e Mon Sep 17 00:00:00 2001 From: Roger Pau Monne Date: Tue, 4 Dec 2012 15:21:53 +0100 Subject: llist/xen-blkfront: implement safe version of llist_for_each_entry MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Implement a safe version of llist_for_each_entry, and use it 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 Signed-off-by: Roger Pau Monné Acked-by: Andrew Morton [v2: Move the llist_for_each_entry_safe in llist.h] Signed-off-by: Konrad Rzeszutek Wilk --- include/linux/llist.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'include') diff --git a/include/linux/llist.h b/include/linux/llist.h index a5199f6d0e8..d0ab98f73d3 100644 --- a/include/linux/llist.h +++ b/include/linux/llist.h @@ -124,6 +124,31 @@ static inline void init_llist_head(struct llist_head *list) &(pos)->member != NULL; \ (pos) = llist_entry((pos)->member.next, typeof(*(pos)), member)) +/** + * llist_for_each_entry_safe - iterate safely against remove over some entries + * of lock-less list of given type. + * @pos: the type * to use as a loop cursor. + * @n: another type * to use as a temporary storage. + * @node: the fist entry of deleted list entries. + * @member: the name of the llist_node with the struct. + * + * In general, some entries of the lock-less list can be traversed + * safely only after being removed from list, so start with an entry + * instead of list head. This variant allows removal of entries + * as we iterate. + * + * If being used on entries deleted from lock-less list directly, the + * traverse order is from the newest to the oldest added entry. If + * you want to traverse from the oldest to the newest, you must + * reverse the order by yourself before traversing. + */ +#define llist_for_each_entry_safe(pos, n, node, member) \ + for ((pos) = llist_entry((node), typeof(*(pos)), member), \ + (n) = (pos)->member.next; \ + &(pos)->member != NULL; \ + (pos) = llist_entry(n, typeof(*(pos)), member), \ + (n) = (&(pos)->member != NULL) ? (pos)->member.next : NULL) + /** * llist_empty - tests whether a lock-less list is empty * @head: the list to test -- cgit v1.2.3