From 7302e91f39a81a9c2efcf4bc5749d18128366945 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 14 Jan 2022 14:03:58 -0800 Subject: [PATCH] mm/slab_common: use WARN() if cache still has objects on destroy Calling kmem_cache_destroy() while the cache still has objects allocated is a kernel bug, and will usually result in the entire cache being leaked. While the message in kmem_cache_destroy() resembles a warning, it is currently not implemented using a real WARN(). This is problematic for infrastructure testing the kernel, all of which rely on the specific format of WARN()s to pick up on bugs. Some 13 years ago this used to be a simple WARN_ON() in slub, but commit d629d8195793 ("slub: improve kmem_cache_destroy() error message") changed it into an open-coded warning to avoid confusion with a bug in slub itself. Instead, turn the open-coded warning into a real WARN() with the message preserved, so that test systems can actually identify these issues, and we get all the other benefits of using a normal WARN(). The warning message is extended with "when called from " to make it even clearer where the fault lies. For most configurations this is only a cosmetic change, however, note that WARN() here will now also respect panic_on_warn. Link: https://lkml.kernel.org/r/20211102170733.648216-1-elver@google.com Signed-off-by: Marco Elver Reviewed-by: Vlastimil Babka Acked-by: David Rientjes Cc: Christoph Lameter Cc: Pekka Enberg Cc: Joonsoo Kim Cc: Dmitry Vyukov Cc: Alexander Potapenko Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/slab_common.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/mm/slab_common.c b/mm/slab_common.c index e5d080a..c6213f1 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -489,8 +489,6 @@ void slab_kmem_cache_release(struct kmem_cache *s) void kmem_cache_destroy(struct kmem_cache *s) { - int err; - if (unlikely(!s)) return; @@ -501,12 +499,9 @@ void kmem_cache_destroy(struct kmem_cache *s) if (s->refcount) goto out_unlock; - err = shutdown_cache(s); - if (err) { - pr_err("%s %s: Slab cache still has objects\n", - __func__, s->name); - dump_stack(); - } + WARN(shutdown_cache(s), + "%s %s: Slab cache still has objects when called from %pS", + __func__, s->name, (void *)_RET_IP_); out_unlock: mutex_unlock(&slab_mutex); cpus_read_unlock(); -- 2.7.4