Route sources have an explicit owner

This commit prevents use-after-free of routes belonging to protocols
which have been already destroyed, delaying also all the protocols'
shutdown until all of their routes have been finally propagated through
all the pipes down to the appropriate exports.

The use-after-free was somehow hypothetic yet theoretically possible in
rare conditions, when one BGP protocol authors a lot of routes and the
user deletes that protocol by reconfiguring in the same time as next hop
update is requested, causing rte_better() to be called on a
not-yet-pruned network prefix while the owner protocol has been already
freed.

In parallel execution environments, this would happen an inter-thread
use-after-free, causing possible heisenbugs or other nasty problems.

1 files changed, 10 insertions, 6 deletions

diff --git a/proto/babel/babel.c b/proto/babel/babel.c
index 03c85b7d..40e85a16 100644
--- a/proto/babel/babel.c
+++ b/proto/babel/babel.c
@@ -2264,7 +2264,7 @@ babel_preexport(struct channel *c, struct rte *new)
 {
   struct rta *a = new->attrs;
   /* Reject our own unreachable routes */
-  if ((a->dest == RTD_UNREACHABLE) && (new->src->proto == c->proto))
+  if ((a->dest == RTD_UNREACHABLE) && (new->src->owner == &c->proto->sources))
     return -1;
 
   return 0;
@@ -2288,7 +2288,7 @@ babel_rt_notify(struct proto *P, struct channel *c UNUSED, const net_addr *net,
     uint rt_metric = ea_get_int(new->attrs->eattrs, EA_BABEL_METRIC, 0);
     u64 rt_router_id = 0;
 
-    if (new->src->proto == P)
+    if (new->src->owner == &P->sources)
     {
       rt_seqno = ea_find(new->attrs->eattrs, EA_BABEL_SEQNO)->u.data;
       eattr *e = ea_find(new->attrs->eattrs, EA_BABEL_ROUTER_ID);
@@ -2372,6 +2372,12 @@ babel_postconfig(struct proto_config *CF)
   cf->ip6_channel = ip6 ?: ip6_sadr;
 }
 
+static struct rte_owner_class babel_rte_owner_class = {
+  .get_route_info =	babel_get_route_info,
+  .rte_better =		babel_rte_better,
+  .rte_igp_metric =	babel_rte_igp_metric,
+};
+
 static struct proto *
 babel_init(struct proto_config *CF)
 {
@@ -2385,8 +2391,8 @@ babel_init(struct proto_config *CF)
   P->if_notify = babel_if_notify;
   P->rt_notify = babel_rt_notify;
   P->preexport = babel_preexport;
-  P->rte_better = babel_rte_better;
-  P->rte_igp_metric = babel_rte_igp_metric;
+
+  P->sources.class = &babel_rte_owner_class;
 
   return P;
 }
@@ -2479,7 +2485,6 @@ babel_reconfigure(struct proto *P, struct proto_config *CF)
   return 1;
 }
 
-
 struct protocol proto_babel = {
   .name =		"Babel",
   .template =		"babel%d",
@@ -2494,6 +2499,5 @@ struct protocol proto_babel = {
   .start =		babel_start,
   .shutdown =		babel_shutdown,
   .reconfigure =	babel_reconfigure,
-  .get_route_info =	babel_get_route_info,
   .get_attr =		babel_get_attr
 };