The patch titled Subject: slub: fix __kmem_cache_empty for !CONFIG_SLUB_DEBUG has been added to the -mm tree. Its filename is slub-fix-__kmem_cache_empty-for-config_slub_debug.patch

This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/slub-fix-__kmem_cache_empty-for-con... and later at http://ozlabs.org/~akpm/mmotm/broken-out/slub-fix-__kmem_cache_empty-for-con...

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------------------------------------------------------ From: Shakeel Butt shakeelb@google.com Subject: slub: fix __kmem_cache_empty for !CONFIG_SLUB_DEBUG

f9e13c0a5a33 ("slab, slub: skip unnecessary kasan_cache_shutdown()") causes crashes when using slub, as described at http://lkml.kernel.org/r/CAHmME9rtoPwxUSnktxzKso14iuVCWT7BE_-_8PAC=pGw1iJnQg...

For !CONFIG_SLUB_DEBUG, SLUB does not maintain the number of slabs allocated per node for a kmem_cache. Thus, slabs_node() in __kmem_cache_empty() will always return 0. So, in such situation, it is required to check per-cpu slabs to make sure if a kmem_cache is empty or not.

Please note that __kmem_cache_shutdown() and __kmem_cache_shrink() are not affected by !CONFIG_SLUB_DEBUG as they call flush_all() to clear per-cpu slabs.

Link: http://lkml.kernel.org/r/20180619213352.71740-1-shakeelb@google.com Link: http://lkml.kernel.org/r/CAHmME9rtoPwxUSnktxzKso14iuVCWT7BE_-_8PAC=pGw1iJnQg... Fixes: f9e13c0a5a33 ("slab, slub: skip unnecessary kasan_cache_shutdown()") Signed-off-by: Shakeel Butt shakeelb@google.com Reported-by: Jason A. Donenfeld Jason@zx2c4.com Tested-by: Jason A. Donenfeld Jason@zx2c4.com Cc: Christoph Lameter cl@linux.com Cc: Pekka Enberg penberg@kernel.org Cc: David Rientjes rientjes@google.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/slub.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)

diff -puN mm/slub.c~slub-fix-__kmem_cache_empty-for-config_slub_debug mm/slub.c --- a/mm/slub.c~slub-fix-__kmem_cache_empty-for-config_slub_debug +++ a/mm/slub.c @@ -3673,9 +3673,23 @@ static void free_partial(struct kmem_cac

bool __kmem_cache_empty(struct kmem_cache *s) { - int node; + int cpu, node; struct kmem_cache_node *n;

+ /* + * slabs_node will always be 0 for !CONFIG_SLUB_DEBUG. So, manually + * check slabs for all cpus. + */ + if (!IS_ENABLED(CONFIG_SLUB_DEBUG)) { + for_each_online_cpu(cpu) { + struct kmem_cache_cpu *c; + + c = per_cpu_ptr(s->cpu_slab, cpu); + if (c->page || slub_percpu_partial(c)) + return false; + } + } + for_each_kmem_cache_node(s, node, n) if (n->nr_partial || slabs_node(s, node)) return false; _

Patches currently in -mm which might be from shakeelb@google.com are

slub-fix-__kmem_cache_empty-for-config_slub_debug.patch