[RFC][PATCH 3/5] mm/dmapool: allow NULL `pool' pointer in dma_pool_destroy()

[Sergey Senozhatsky]

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

	if (pool)
		dma_pool_destroy(pool);

Or, otherwise, be invalid dma_pool_destroy() users.

Tweak dma_pool_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/dmapool.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/dmapool.c b/mm/dmapool.c
index fd5fe43..5f2cffc 100644
--- a/mm/dmapool.c
+++ b/mm/dmapool.c
@@ -271,6 +271,9 @@ void dma_pool_destroy(struct dma_pool *pool)
 {
 	bool empty = false;
 
+	if (unlikely(!pool))
+		return;
+
 	mutex_lock(&pools_reg_lock);
 	mutex_lock(&pools_lock);
 	list_del(&pool->pools);
-- 
2.4.3.368.g7974889

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