Avoid free()ing from an mmap on corrupted microdesc cache

The 'body' field of a microdesc_t holds a strdup()'d value if the
microdesc's saved_location field is SAVED_IN_JOURNAL or
SAVED_NOWHERE, and holds a pointer to the middle of an mmap if the
microdesc is SAVED_IN_CACHE.  But we weren't setting that field
until a while after we parsed the microdescriptor, which left an
interval where microdesc_free() would try to free() the middle of
the mmap().

This patch also includes a regression test.

This is a fix for #10409; bugfix on 0.2.2.6-alpha.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/or/microdesc.c b/src/or/microdesc.c
index b4d22c1c62..6f9134cf29 100644
--- a/src/or/microdesc.c
+++ b/src/or/microdesc.c
@@ -149,11 +149,10 @@ microdescs_add_to_cache(microdesc_cache_t *cache,
 {
   smartlist_t *descriptors, *added;
   const int allow_annotations = (where != SAVED_NOWHERE);
-  const int copy_body = (where != SAVED_IN_CACHE);
 
   descriptors = microdescs_parse_from_string(s, eos,
                                              allow_annotations,
-                                             copy_body);
+                                             where);
   if (listed_at > 0) {
     SMARTLIST_FOREACH(descriptors, microdesc_t *, md,
                       md->last_listed = listed_at);