lib/genalloc.c: check result of devres_alloc()

devm_gen_pool_create() calls devres_alloc() and dereferences its result
without checking whether devres_alloc() succeeded.  Check for error and
bail out if it happened.

Coverity-id 1016493.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lib/genalloc.c

@@ -586,6 +586,8 @@ struct gen_pool *devm_gen_pool_create(struct device *dev, int min_alloc_order,
 	struct gen_pool **ptr, *pool;
 
 	ptr = devres_alloc(devm_gen_pool_release, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return NULL;
 
 	pool = gen_pool_create(min_alloc_order, nid);
 	if (pool) {