From 5c4cf3fcc43a481d77c22cf3c70c736467651cd3 Mon Sep 17 00:00:00 2001 From: Evan Hunt Date: Wed, 27 Apr 2022 22:12:01 -0700 Subject: [PATCH] prevent a deadlock in the shutdown system test The shutdown test sends 'rdnc status' commands in parallel with 'rndc stop' A new rndc connection arriving will reference the ACL environment to see whether the client is allowed to connect. Commit c0995bc380 added a mutex lock to ns_interfacemgr_getaclenv(), but if the new connection arrives while the interfaces are being purged during shutdown, that lock is already being held. If the the connection event slips in ahead of one of the netmgr's "stop listening" events on a worker thread, a deadlock can occur. The fix is not to hold the interfacemgr lock while shutting down interfaces; only while actually traversing the interface list to identify interfaces needing shutdown. --- lib/ns/interfacemgr.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/lib/ns/interfacemgr.c b/lib/ns/interfacemgr.c index d62b8d92d4..7b5093e13b 100644 --- a/lib/ns/interfacemgr.c +++ b/lib/ns/interfacemgr.c @@ -742,10 +742,6 @@ interface_destroy(ns_interface_t **interfacep) { ns_interface_shutdown(ifp); - if (ISC_LINK_LINKED(ifp, link)) { - ISC_LIST_UNLINK(mgr->interfaces, ifp, link); - } - ifp->magic = 0; isc_mutex_destroy(&ifp->lock); ns_interfacemgr_detach(&ifp->mgr); @@ -779,26 +775,34 @@ find_matching_interface(ns_interfacemgr_t *mgr, isc_sockaddr_t *addr) { */ static void purge_old_interfaces(ns_interfacemgr_t *mgr) { - ns_interface_t *ifp, *next; + ns_interface_t *ifp = NULL, *next = NULL; + ISC_LIST(ns_interface_t) interfaces; + + ISC_LIST_INIT(interfaces); + LOCK(&mgr->lock); for (ifp = ISC_LIST_HEAD(mgr->interfaces); ifp != NULL; ifp = next) { INSIST(NS_INTERFACE_VALID(ifp)); next = ISC_LIST_NEXT(ifp, link); if (ifp->generation != mgr->generation) { ISC_LIST_UNLINK(ifp->mgr->interfaces, ifp, link); - if (LISTENING(ifp)) { - char sabuf[256]; - isc_sockaddr_format(&ifp->addr, sabuf, - sizeof(sabuf)); - isc_log_write( - IFMGR_COMMON_LOGARGS, ISC_LOG_INFO, - "no longer listening on %s", sabuf); - ns_interface_shutdown(ifp); - } - interface_destroy(&ifp); + ISC_LIST_APPEND(interfaces, ifp, link); } } UNLOCK(&mgr->lock); + + for (ifp = ISC_LIST_HEAD(interfaces); ifp != NULL; ifp = next) { + next = ISC_LIST_NEXT(ifp, link); + if (LISTENING(ifp)) { + char sabuf[256]; + isc_sockaddr_format(&ifp->addr, sabuf, sizeof(sabuf)); + isc_log_write(IFMGR_COMMON_LOGARGS, ISC_LOG_INFO, + "no longer listening on %s", sabuf); + ns_interface_shutdown(ifp); + } + ISC_LIST_UNLINK(interfaces, ifp, link); + interface_destroy(&ifp); + } } static bool