From: Christopher Lameter <cl@xxxxxxxxx> Subject: slub: remove kmalloc under list_lock from list_slab_objects() V2 list_slab_objects() is called when a slab is destroyed and there are objects still left to list the objects in the syslog. This is a pretty rare event. And there it seems we take the list_lock and call kmalloc while holding that lock. Perform the allocation in free_partial() before the list_lock is taken. Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2002031721250.1668@xxxxxxxxxxxxxxx Fixes: bbd7d57bfe852d9788bae5fb171c7edb4021d8ac ("slub: Potential stack overflow") Signed-off-by: Christopher Lameter <cl@xxxxxxxxx> Cc: Pekka Enberg <penberg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Yu Zhao <yuzhao@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/slub.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) --- a/mm/slub.c~slub-remove-kmalloc-under-list_lock-from-list_slab_objects +++ a/mm/slub.c @@ -3766,12 +3766,14 @@ error: } static void list_slab_objects(struct kmem_cache *s, struct page *page, - const char *text) + const char *text, unsigned long *map) { #ifdef CONFIG_SLUB_DEBUG void *addr = page_address(page); void *p; - unsigned long *map; + + if (!map) + return; slab_err(s, page, text, s->name); slab_lock(page); @@ -3784,8 +3786,6 @@ static void list_slab_objects(struct kme print_tracking(s, p); } } - put_map(map); - slab_unlock(page); #endif } @@ -3799,6 +3799,11 @@ static void free_partial(struct kmem_cac { LIST_HEAD(discard); struct page *page, *h; + unsigned long *map = NULL; + +#ifdef CONFIG_SLUB_DEBUG + map = bitmap_alloc(oo_objects(s->max), GFP_KERNEL); +#endif BUG_ON(irqs_disabled()); spin_lock_irq(&n->list_lock); @@ -3808,11 +3813,16 @@ static void free_partial(struct kmem_cac list_add(&page->slab_list, &discard); } else { list_slab_objects(s, page, - "Objects remaining in %s on __kmem_cache_shutdown()"); + "Objects remaining in %s on __kmem_cache_shutdown()", + map); } } spin_unlock_irq(&n->list_lock); +#ifdef CONFIG_SLUB_DEBUG + bitmap_free(map); +#endif + list_for_each_entry_safe(page, h, &discard, slab_list) discard_slab(s, page); } _
