From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 14 Sep 2012 14:10:16 +0000 (-0400)
Subject: document why we only allow 64 flags in votes
X-Git-Tag: tor-0.2.4.3-alpha~31^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=68caa834f4ed9cae16a551c9fc63ea982c9f1904;p=thirdparty%2Ftor.git

document why we only allow 64 flags in votes
---

diff --git a/src/or/routerparse.c b/src/or/routerparse.c
index 496b90d4ad..43a95e88c1 100644
--- a/src/or/routerparse.c
+++ b/src/or/routerparse.c
@@ -3006,6 +3006,11 @@ networkstatus_parse_vote_from_string(const char *s, const char **eos_out,
   }
   if (ns->type != NS_TYPE_CONSENSUS &&
       smartlist_len(ns->known_flags) > MAX_KNOWN_FLAGS_IN_VOTE) {
+    /* If we allowed more than 64 flags in votes, then parsing them would make
+     * us invoke undefined behavior whenever we used 1<<flagnum to do a
+     * bit-shift. This is only for votes and opinions: consensus users don't
+     * care about flags they don't recognize, and so don't build a bitfield
+     * for them. */
     log_warn(LD_DIR, "Too many known-flags in consensus vote or opinion");
     goto err;
   }