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, 2 insertions, 1 deletions

diff --git a/src/or/dirvote.c b/src/or/dirvote.c
index 144859ae04..ab2225cf02 100644
--- a/src/or/dirvote.c
+++ b/src/or/dirvote.c
@@ -3538,7 +3538,8 @@ dirvote_create_microdescriptor(const routerinfo_t *ri)
 
   {
     smartlist_t *lst = microdescs_parse_from_string(output,
-                                                 output+strlen(output), 0, 1);
+                                                 output+strlen(output), 0,
+                                                    SAVED_NOWHERE);
     if (smartlist_len(lst) != 1) {
       log_warn(LD_DIR, "We generated a microdescriptor we couldn't parse.");
       SMARTLIST_FOREACH(lst, microdesc_t *, md, microdesc_free(md));