[PATCH v3 07/18] tailq: fix cast macro for null pointer

[David Marchand]

Doing arithmetic with the NULL pointer is undefined.

Caught by UBSan:

../app/test/test_tailq.c:111:9: runtime error:
	member access within null pointer of type 'struct rte_tailq_head'

Fixes: f6b4f6c9c123 ("tailq: use a single cast macro")
Cc: stable at dpdk.org

Signed-off-by: David Marchand <david.marchand at redhat.com>
Acked-by: Bruce Richardson <bruce.richardson at intel.com>
---
 lib/eal/include/rte_tailq.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/eal/include/rte_tailq.h b/lib/eal/include/rte_tailq.h
index 89f7ef2134..c23df77d96 100644
--- a/lib/eal/include/rte_tailq.h
+++ b/lib/eal/include/rte_tailq.h
@@ -54,7 +54,7 @@ struct rte_tailq_elem {
  * Return the first tailq entry cast to the right struct.
  */
 #define RTE_TAILQ_CAST(tailq_entry, struct_name) \
-	(struct struct_name *)&(tailq_entry)->tailq_head
+	(tailq_entry == NULL ? NULL : (struct struct_name *)&(tailq_entry)->tailq_head)
 
 /**
  * Utility macro to make looking up a tailqueue for a particular struct easier.
-- 
2.50.0