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authorMuchun Song <songmuchun@bytedance.com>2020-07-24 07:15:27 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-07-24 22:42:41 +0300
commitd38a2b7a9c939e6d7329ab92b96559ccebf7b135 (patch)
tree160c2e50d11e032e35e531b4a3ba15a8d21b6583
parent8d22a9351035ef2ff12ef163a1091b8b8cf1e49c (diff)
downloadlinux-sunxi-d38a2b7a9c939e6d7329ab92b96559ccebf7b135.tar.xz
mm: memcg/slab: fix memory leak at non-root kmem_cache destroy
If the kmem_cache refcount is greater than one, we should not mark the root kmem_cache as dying. If we mark the root kmem_cache dying incorrectly, the non-root kmem_cache can never be destroyed. It resulted in memory leak when memcg was destroyed. We can use the following steps to reproduce. 1) Use kmem_cache_create() to create a new kmem_cache named A. 2) Coincidentally, the kmem_cache A is an alias for kmem_cache B, so the refcount of B is just increased. 3) Use kmem_cache_destroy() to destroy the kmem_cache A, just decrease the B's refcount but mark the B as dying. 4) Create a new memory cgroup and alloc memory from the kmem_cache B. It leads to create a non-root kmem_cache for allocating memory. 5) When destroy the memory cgroup created in the step 4), the non-root kmem_cache can never be destroyed. If we repeat steps 4) and 5), this will cause a lot of memory leak. So only when refcount reach zero, we mark the root kmem_cache as dying. Fixes: 92ee383f6daa ("mm: fix race between kmem_cache destroy, create and deactivate") Signed-off-by: Muchun Song <songmuchun@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Acked-by: Roman Gushchin <guro@fb.com> Cc: Vlastimil Babka <vbabka@suse.cz> 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: Shakeel Butt <shakeelb@google.com> Cc: <stable@vger.kernel.org> Link: http://lkml.kernel.org/r/20200716165103.83462-1-songmuchun@bytedance.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/slab_common.c35
1 files changed, 28 insertions, 7 deletions
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 37d48a56431d..fe8b68482670 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -326,6 +326,14 @@ int slab_unmergeable(struct kmem_cache *s)
if (s->refcount < 0)
return 1;
+#ifdef CONFIG_MEMCG_KMEM
+ /*
+ * Skip the dying kmem_cache.
+ */
+ if (s->memcg_params.dying)
+ return 1;
+#endif
+
return 0;
}
@@ -886,12 +894,15 @@ static int shutdown_memcg_caches(struct kmem_cache *s)
return 0;
}
-static void flush_memcg_workqueue(struct kmem_cache *s)
+static void memcg_set_kmem_cache_dying(struct kmem_cache *s)
{
spin_lock_irq(&memcg_kmem_wq_lock);
s->memcg_params.dying = true;
spin_unlock_irq(&memcg_kmem_wq_lock);
+}
+static void flush_memcg_workqueue(struct kmem_cache *s)
+{
/*
* SLAB and SLUB deactivate the kmem_caches through call_rcu. Make
* sure all registered rcu callbacks have been invoked.
@@ -923,10 +934,6 @@ static inline int shutdown_memcg_caches(struct kmem_cache *s)
{
return 0;
}
-
-static inline void flush_memcg_workqueue(struct kmem_cache *s)
-{
-}
#endif /* CONFIG_MEMCG_KMEM */
void slab_kmem_cache_release(struct kmem_cache *s)
@@ -944,8 +951,6 @@ void kmem_cache_destroy(struct kmem_cache *s)
if (unlikely(!s))
return;
- flush_memcg_workqueue(s);
-
get_online_cpus();
get_online_mems();
@@ -955,6 +960,22 @@ void kmem_cache_destroy(struct kmem_cache *s)
if (s->refcount)
goto out_unlock;
+#ifdef CONFIG_MEMCG_KMEM
+ memcg_set_kmem_cache_dying(s);
+
+ mutex_unlock(&slab_mutex);
+
+ put_online_mems();
+ put_online_cpus();
+
+ flush_memcg_workqueue(s);
+
+ get_online_cpus();
+ get_online_mems();
+
+ mutex_lock(&slab_mutex);
+#endif
+
err = shutdown_memcg_caches(s);
if (!err)
err = shutdown_cache(s);