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 fbd33cc3ff346c704ae264d724563977a5ff473f..16f7d1cdaa433d47f72aecd31a20b3a99cc2a8fe 100644 (file)
--- 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
 }