From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 22 Jun 2023 13:59:53 +0000 (-0400)
Subject: Avoid calling caa_container_of on NULL pointer in cds_lfht macros
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=e58cdfcfc3884d003b7a0b097fd02c6969382edc;p=userspace-rcu.git

Avoid calling caa_container_of on NULL pointer in cds_lfht macros

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. Introduce the cds_lfht_entry() macro to eliminate code
duplication.

Reported-by: Ondřej Surý <ondrej@sury.org>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9969c1e0bc0eefc8c90c0d8f17b2927f6a4feb2a
---

diff --git a/include/urcu/rculfhash.h b/include/urcu/rculfhash.h
index fbd33cc..16f7d1c 100644
--- a/include/urcu/rculfhash.h
+++ b/include/urcu/rculfhash.h
@@ -544,24 +544,30 @@ void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size);
 		cds_lfht_next_duplicate(ht, match, key, iter),		\
 			node = cds_lfht_iter_get_node(iter))
 
+#define cds_lfht_entry(ptr, type, member)				\
+	({								\
+		caa_unqual_scalar_typeof(ptr) ___ptr = (ptr);		\
+		___ptr ? caa_container_of(___ptr, type, member) : NULL;	\
+	})
+
 #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_entry(cds_lfht_iter_get_node(iter), \
+				__typeof__(*(pos)), member);		\
+		pos != NULL;						\
 		cds_lfht_next(ht, iter),				\
-			pos = caa_container_of(cds_lfht_iter_get_node(iter), \
-					__typeof__(*(pos)), member))
+			pos = cds_lfht_entry(cds_lfht_iter_get_node(iter), \
+				__typeof__(*(pos)), member))
 
 #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_entry(cds_lfht_iter_get_node(iter), \
+				__typeof__(*(pos)), member);		\
+		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_entry(cds_lfht_iter_get_node(iter), \
+				__typeof__(*(pos)), member))
 
 #ifdef __cplusplus
 }