[lttng-dev] [PATCH] Avoid calling caa_container_of on NULL pointer in cds_lfhash macros

[Ondřej Surý]

The cds_lfht_for_each_entry and cds_lfht_for_each_entry_duplicate macros
would call caa_container_of() macro on NULL pointer.  This is not a
problem under normal circumstances as the check in the for loop fails
and the loop-statement is not called with invalid (pos) value.

However AddressSanitizer doesn't like that and complains about this:

    runtime error: applying non-zero offset 18446744073709551056 to null pointer

Move the cds_lfht_iter_get_node(iter) != NULL from the cond-expression
of the for loop into both init-clause and iteration-expression as
conditional operator and check for (pos) value in the cond-expression
instead.

Signed-off-by: Ondřej Surý <ondrej at sury.org>
---
 include/urcu/rculfhash.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/urcu/rculfhash.h b/include/urcu/rculfhash.h
index fbd33cc..aafc455 100644
--- a/include/urcu/rculfhash.h
+++ b/include/urcu/rculfhash.h
@@ -546,22 +546,22 @@ void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 
 #define cds_lfht_for_each_entry(ht, iter, pos, member)			\
 	for (cds_lfht_first(ht, iter),					\
-			pos = caa_container_of(cds_lfht_iter_get_node(iter), \
-					__typeof__(*(pos)), member);	\
-		cds_lfht_iter_get_node(iter) != NULL;			\
+			pos = (cds_lfht_iter_get_node(iter) != NULL ? caa_container_of(cds_lfht_iter_get_node(iter), \
+					__typeof__(*(pos)), member) : NULL);	\
+		pos != NULL;			\
 		cds_lfht_next(ht, iter),				\
-			pos = caa_container_of(cds_lfht_iter_get_node(iter), \
-					__typeof__(*(pos)), member))
+			pos = (cds_lfht_iter_get_node(iter) != NULL ? caa_container_of(cds_lfht_iter_get_node(iter), \
+					__typeof__(*(pos)), member) : NULL)
 
 #define cds_lfht_for_each_entry_duplicate(ht, hash, match, key,		\
 				iter, pos, member)			\
 	for (cds_lfht_lookup(ht, hash, match, key, iter),		\
-			pos = caa_container_of(cds_lfht_iter_get_node(iter), \
-					__typeof__(*(pos)), member);	\
-		cds_lfht_iter_get_node(iter) != NULL;			\
+			pos = (cds_lfht_iter_get_node(iter) != NULL ? caa_container_of(cds_lfht_iter_get_node(iter), \
+					__typeof__(*(pos)), member) : NULL);	\
+		pos != NULL;			\
 		cds_lfht_next_duplicate(ht, match, key, iter),		\
-			pos = caa_container_of(cds_lfht_iter_get_node(iter), \
-					__typeof__(*(pos)), member))
+			pos = (cds_lfht_iter_get_node(iter) != NULL ? caa_container_of(cds_lfht_iter_get_node(iter), \
+					__typeof__(*(pos)), member) : NULL)
 
 #ifdef __cplusplus
 }
-- 
2.39.2