From: Josef Bacik Date: Fri, 28 Apr 2017 13:49:19 +0000 (-0400) Subject: nbd: fix use after free on module unload X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=60ae36ad0340b1ba88530d6a5e141455dd3afd81;p=linux.git 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 --- diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 5583dc4ff9415..ac376b9b852d6 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);