[patch 01/37] fix RCU-callback-after-kmem_cache_destroy problem in sl[aou]b

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>

commit 7ed9f7e5db58c6e8c2b4b738a75d5dcd8e17aad5 upstream.

Jesper noted that kmem_cache_destroy() invokes synchronize_rcu() rather than
rcu_barrier() in the SLAB_DESTROY_BY_RCU case, which could result in RCU
callbacks accessing a kmem_cache after it had been destroyed.

Acked-by: Matt Mackall <mpm@xxxxxxxxxxx>
Reported-by: Jesper Dangaard Brouer <hawk@xxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 mm/slab.c |    2 +-
 mm/slob.c |    2 ++
 mm/slub.c |    2 ++
 3 files changed, 5 insertions(+), 1 deletion(-)

--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2580,7 +2580,7 @@ void kmem_cache_destroy(struct kmem_cach
 	}
 
 	if (unlikely(cachep->flags & SLAB_DESTROY_BY_RCU))
-		synchronize_rcu();
+		rcu_barrier();
 
 	__kmem_cache_destroy(cachep);
 	mutex_unlock(&cache_chain_mutex);
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -561,6 +561,8 @@ EXPORT_SYMBOL(kmem_cache_create);
 
 void kmem_cache_destroy(struct kmem_cache *c)
 {
+	if (c->flags & SLAB_DESTROY_BY_RCU)
+		rcu_barrier();
 	slob_free(c, sizeof(struct kmem_cache));
 }
 EXPORT_SYMBOL(kmem_cache_destroy);
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2447,6 +2447,8 @@ static inline int kmem_cache_close(struc
  */
 void kmem_cache_destroy(struct kmem_cache *s)
 {
+	if (s->flags & SLAB_DESTROY_BY_RCU)
+		rcu_barrier();
 	down_write(&slub_lock);
 	s->refcount--;
 	if (!s->refcount) {


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