[RFC][PATCH 2/5] mm/mempool: allow NULL `pool' pointer in mempool_destroy()

[Sergey Senozhatsky]

mempool_destroy() does not tolerate a NULL mempool_t pointer
argument and performs a NULL-pointer dereference. This requires
additional attention and effort from developers/reviewers and
forces all mempool_destroy() callers to do a NULL check

	if (pool)
		mempool_destroy(pool);

Or, otherwise, be invalid mempool_destroy() users.

Tweak mempool_destroy() and NULL-check the pointer there.

Proposed by Andrew Morton.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
LKML-reference: https://lkml.org/lkml/2015/6/8/583
---
 mm/mempool.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/mempool.c b/mm/mempool.c
index 2cc08de..4c533bc 100644
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -150,6 +150,9 @@ static void *remove_element(mempool_t *pool)
  */
 void mempool_destroy(mempool_t *pool)
 {
+	if (unlikely(!pool))
+		return;
+
 	while (pool->curr_nr) {
 		void *element = remove_element(pool);
 		pool->free(element, pool->pool_data);
-- 
2.4.3.368.g7974889

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