From 4442f60d8e959e9983e58ff534e7302ebf2f9d7e Mon Sep 17 00:00:00 2001 From: Chunwei Chen Date: Mon, 23 May 2016 11:58:21 -0700 Subject: [PATCH] Fix arc_prune_task use-after-free arc_prune_task uses a refcount to protect arc_prune_t, but it doesn't prevent the underlying zsb from disappearing if there's a concurrent umount. We fix this by force the caller of arc_remove_prune_callback to wait for arc_prune_taskq to finish. Signed-off-by: Chunwei Chen Signed-off-by: Brian Behlendorf Closes #4687 Closes #4690 --- module/zfs/arc.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/module/zfs/arc.c b/module/zfs/arc.c index 716ba5c2d9..18e9a145d3 100644 --- a/module/zfs/arc.c +++ b/module/zfs/arc.c @@ -2707,12 +2707,7 @@ arc_prune_task(void *ptr) if (func != NULL) func(ap->p_adjust, ap->p_private); - /* Callback unregistered concurrently with execution */ - if (refcount_remove(&ap->p_refcnt, func) == 0) { - ASSERT(!list_link_active(&ap->p_node)); - refcount_destroy(&ap->p_refcnt); - kmem_free(ap, sizeof (*ap)); - } + refcount_remove(&ap->p_refcnt, func); } /* @@ -4628,13 +4623,19 @@ arc_add_prune_callback(arc_prune_func_t *func, void *private) void arc_remove_prune_callback(arc_prune_t *p) { + boolean_t wait = B_FALSE; mutex_enter(&arc_prune_mtx); list_remove(&arc_prune_list, p); - if (refcount_remove(&p->p_refcnt, &arc_prune_list) == 0) { - refcount_destroy(&p->p_refcnt); - kmem_free(p, sizeof (*p)); - } + if (refcount_remove(&p->p_refcnt, &arc_prune_list) > 0) + wait = B_TRUE; mutex_exit(&arc_prune_mtx); + + /* wait for arc_prune_task to finish */ + if (wait) + taskq_wait_outstanding(arc_prune_taskq, 0); + ASSERT0(refcount_count(&p->p_refcnt)); + refcount_destroy(&p->p_refcnt); + kmem_free(p, sizeof (*p)); } void