[Tarantool-patches] [PATCH] Memtx_tuple_delete used heap after free

[Maria <maria.khaydich@tarantool.org>]

Struct of type tuple_format is being passed as
an argument to tuple_format_unref where it might
be freed. On such occasion any further references
to format fields should not take place.

Closes #4658
---
Issue:
https://github.com/tarantool/tarantool/issues/4658
Branch:
https://github.com/tarantool/tarantool/compare/eljashm/gh-4658-heap-use-after-free

 src/box/memtx_engine.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/box/memtx_engine.c b/src/box/memtx_engine.c
index 23ccc4703..bdce4ac32 100644
--- a/src/box/memtx_engine.c
+++ b/src/box/memtx_engine.c
@@ -1177,13 +1177,13 @@ memtx_tuple_delete(struct tuple_format *format, struct tuple *tuple)
 	struct memtx_engine *memtx = (struct memtx_engine *)format->engine;
 	say_debug("%s(%p)", __func__, tuple);
 	assert(tuple->refs == 0);
+	bool is_temp = format->is_temporary;
 	tuple_format_unref(format);
 	struct memtx_tuple *memtx_tuple =
 		container_of(tuple, struct memtx_tuple, base);
 	size_t total = tuple_size(tuple) + offsetof(struct memtx_tuple, base);
 	if (memtx->alloc.free_mode != SMALL_DELAYED_FREE ||
-	    memtx_tuple->version == memtx->snapshot_version ||
-	    format->is_temporary)
+	    memtx_tuple->version == memtx->snapshot_version || is_temp)
 		smfree(&memtx->alloc, memtx_tuple, total);
 	else
 		smfree_delayed(&memtx->alloc, memtx_tuple, total);
-- 
2.20.1 (Apple Git-117)