From 5903c6bd1a48d90b99e207ec2a6a7673cbbb732d Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Tue, 2 Sep 2014 15:21:30 +0100 Subject: xen/gntalloc: safely delete grefs in add_grefs() undo path If a gref could not be added (perhaps because the limit has been reached or there are no more grant references available), the undo path may crash because __del_gref() frees the gref while it is being used for a list iteration. A comment suggests that using list_for_each_entry() is safe since the gref isn't removed from the list being iterated over, but it is freed and thus list_for_each_entry_safe() must be used. Also, explicitly delete the gref from the local per-file list, even though this is not strictly necessary. Signed-off-by: David Vrabel Reviewed-by: Boris Ostrovsky --- drivers/xen/gntalloc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'drivers/xen/gntalloc.c') diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c index 8ed2bb4f6f21..e53fe191738c 100644 --- a/drivers/xen/gntalloc.c +++ b/drivers/xen/gntalloc.c @@ -124,7 +124,7 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op, int i, rc, readonly; LIST_HEAD(queue_gref); LIST_HEAD(queue_file); - struct gntalloc_gref *gref; + struct gntalloc_gref *gref, *next; readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE); rc = -ENOMEM; @@ -160,8 +160,8 @@ undo: mutex_lock(&gref_mutex); gref_size -= (op->count - i); - list_for_each_entry(gref, &queue_file, next_file) { - /* __del_gref does not remove from queue_file */ + list_for_each_entry_safe(gref, next, &queue_file, next_file) { + list_del(&gref->next_file); __del_gref(gref); } -- cgit