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[tor-commits] [tor/release-0.2.8] Don't look at any routerstatus_t when the networkstatus is inconsistent
commit 9b5a19c64b8195298753b3cd7059e8fcaaabe5bd
Author: Nick Mathewson <nickm@xxxxxxxxxxxxxx>
Date: Mon Sep 19 12:03:58 2016 -0400
Don't look at any routerstatus_t when the networkstatus is inconsistent
For a brief moment in networkstatus_set_current_consensus(), the old
consensus has been freed, but the node_t objects still have dead
pointers to the routerstatus_t objects within it. During that
interval, we absolutely must not do anything that would cause Tor to
look at those dangling pointers.
Unfortunately, calling the (badly labeled!) current_consensus macro
or anything else that calls into we_use_microdescriptors_for_circuits(),
can make us look at the nodelist.
The fix is to make sure we identify the main consensus flavor
_outside_ the danger zone, and to make the danger zone much much
smaller.
Fixes bug 20103. This bug has been implicitly present for AGES; we
just got lucky for a very long time. It became a crash bug in
0.2.8.2-alpha when we merged 35bbf2e4a4e8ccb to make
find_dl_schedule start looking at the consensus, and 4460feaf2850ef0
which made node_get_all_orports less (accidentally) tolerant of
nodes with a valid ri pointer but dangling rs pointer.
---
changes/bug20103 | 7 +++++++
src/or/networkstatus.c | 24 +++++++++++++-----------
2 files changed, 20 insertions(+), 11 deletions(-)
diff --git a/changes/bug20103 b/changes/bug20103
new file mode 100644
index 0000000..c2b81d3
--- /dev/null
+++ b/changes/bug20103
@@ -0,0 +1,7 @@
+ o Major bug fixes (crash):
+
+ - Fix a complicated crash bug that could affect Tor clients
+ configured to use bridges when replacing a networkstatus consensus
+ in which one of their bridges was mentioned. OpenBSD users saw
+ more crashes here, but all platforms were potentially affected.
+ Fixes bug 20103; bugfix on 0.2.8.2-alpha.
diff --git a/src/or/networkstatus.c b/src/or/networkstatus.c
index 51fc011..1cedfef 100644
--- a/src/or/networkstatus.c
+++ b/src/or/networkstatus.c
@@ -1631,7 +1631,9 @@ networkstatus_set_current_consensus(const char *consensus,
if (r != 1 && dl_certs)
authority_certs_fetch_missing(c, now);
- if (flav == usable_consensus_flavor()) {
+ const int is_usable_flavor = flav == usable_consensus_flavor();
+
+ if (is_usable_flavor) {
notify_control_networkstatus_changed(current_consensus, c);
}
if (flav == FLAV_NS) {
@@ -1674,20 +1676,12 @@ networkstatus_set_current_consensus(const char *consensus,
}
}
- /* Reset the failure count only if this consensus is actually valid. */
- if (c->valid_after <= now && now <= c->valid_until) {
- download_status_reset(&consensus_dl_status[flav]);
- } else {
- if (!from_cache)
- download_status_failed(&consensus_dl_status[flav], 0);
- }
+ if (is_usable_flavor) {
+ nodelist_set_consensus(c);
- if (flav == usable_consensus_flavor()) {
/* XXXXNM Microdescs: needs a non-ns variant. ???? NM*/
update_consensus_networkstatus_fetch_time(now);
- nodelist_set_consensus(current_consensus);
-
dirvote_recalculate_timing(options, now);
routerstatus_list_update_named_server_map();
@@ -1711,6 +1705,14 @@ networkstatus_set_current_consensus(const char *consensus,
current_consensus);
}
+ /* Reset the failure count only if this consensus is actually valid. */
+ if (c->valid_after <= now && now <= c->valid_until) {
+ download_status_reset(&consensus_dl_status[flav]);
+ } else {
+ if (!from_cache)
+ download_status_failed(&consensus_dl_status[flav], 0);
+ }
+
if (directory_caches_dir_info(options)) {
dirserv_set_cached_consensus_networkstatus(consensus,
flavor,
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