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Lock zone before checking whether its asynchronous load is already pending

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While this is not an issue in named, which only calls
dns_zone_asyncload() from task-exclusive mode, this function is exported
by libdns and thus may in theory be concurrently called for the same
zone by multiple threads.  It also does not hurt to be consistent
locking-wise with other DNS_ZONEFLG_LOADPENDING accesses.
This commit is contained in:
Michał Kępień
2018-02-15 20:31:49 +01:00
parent 3548061d03
commit 0e4fba2ced
1 changed files with 5 additions and 2 deletions
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7
lib/dns/zone.c
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@@ -2211,8 +2211,11 @@ dns_zone_asyncload(dns_zone_t *zone, dns_zt_zoneloaded_t done, void *arg) {
return (ISC_R_FAILURE);
/* If we already have a load pending, stop now */
if (DNS_ZONE_FLAG(zone, DNS_ZONEFLG_LOADPENDING))
LOCK_ZONE(zone);
if (DNS_ZONE_FLAG(zone, DNS_ZONEFLG_LOADPENDING)) {
UNLOCK_ZONE(zone);
return (ISC_R_ALREADYRUNNING);
}
asl = isc_mem_get(zone->mctx, sizeof (*asl));
if (asl == NULL)
@@ -2229,7 +2232,6 @@ dns_zone_asyncload(dns_zone_t *zone, dns_zt_zoneloaded_t done, void *arg) {
if (e == NULL)
CHECK(ISC_R_NOMEMORY);
LOCK_ZONE(zone);
zone_iattach(zone, &asl->zone);
DNS_ZONE_SETFLAG(zone, DNS_ZONEFLG_LOADPENDING);
isc_task_send(zone->loadtask, &e);
@@ -2240,6 +2242,7 @@ dns_zone_asyncload(dns_zone_t *zone, dns_zt_zoneloaded_t done, void *arg) {
failure:
if (asl != NULL)
isc_mem_put(zone->mctx, asl, sizeof (*asl));
UNLOCK_ZONE(zone);
return (result);
}