From 60ae36ad0340b1ba88530d6a5e141455dd3afd81 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Fri, 28 Apr 2017 09:49:19 -0400 Subject: nbd: fix use after free on module unload list_for_each_entry() isn't super safe if we're freeing the objects while we traverse the list. Also don't bother taking the extra reference, the module refcounting stuff will save us from having anybody messing with the device while we're trying to unload. Reported-by: Ming Lei Signed-off-by: Josef Bacik Signed-off-by: Jens Axboe --- drivers/block/nbd.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 5583dc4ff941..ac376b9b852d 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -2090,7 +2090,6 @@ static int nbd_exit_cb(int id, void *ptr, void *data) struct list_head *list = (struct list_head *)data; struct nbd_device *nbd = ptr; - refcount_inc(&nbd->refs); list_add_tail(&nbd->list, list); return 0; } @@ -2106,11 +2105,12 @@ static void __exit nbd_cleanup(void) idr_for_each(&nbd_index_idr, &nbd_exit_cb, &del_list); mutex_unlock(&nbd_index_mutex); - list_for_each_entry(nbd, &del_list, list) { - if (refcount_read(&nbd->refs) != 2) + while (!list_empty(&del_list)) { + nbd = list_first_entry(&del_list, struct nbd_device, list); + list_del_init(&nbd->list); + if (refcount_read(&nbd->refs) != 1) printk(KERN_ERR "nbd: possibly leaking a device\n"); nbd_put(nbd); - nbd_put(nbd); } idr_destroy(&nbd_index_idr); -- cgit v1.2.3