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Fix race condition on check_stale_header

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This commit fix a race that could happen when two or more threads have
failed to refresh the same RRset, the threads could simultaneously
attempt to update the header->last_refresh_fail_ts field in
check_stale_header, a field used to implement stale-refresh-time.

By making this field atomic we avoid such race.
This commit is contained in:
Diego Fronza 2021-01-27 19:09:46 -03:00 committed by Matthijs Mekking
parent 0fab6cf88e
commit c75575e350
1 changed files with 7 additions and 3 deletions
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10
lib/dns/rbtdb.c
View file

@ -205,7 +205,7 @@ typedef struct rdatasetheader {
rbtdb_rdatatype_t type;
atomic_uint_least16_t attributes;
dns_trust_t trust;
isc_stdtime_t last_refresh_fail_ts;
atomic_uint_fast32_t last_refresh_fail_ts;
struct noqname *noqname;
struct noqname *closest;
unsigned int is_mmapped : 1;
@ -1487,6 +1487,7 @@ init_rdataset(dns_rbtdb_t *rbtdb, rdatasetheader_t *h) {
h->next_is_relative = 0;
h->node_is_relative = 0;
atomic_init(&h->attributes, 0);
atomic_init(&h->last_refresh_fail_ts, 0);
#ifndef ISC_MUTEX_ATOMICS
STATIC_ASSERT((sizeof(h->attributes) == 2),
@ -4571,11 +4572,14 @@ check_stale_header(dns_rbtnode_t *node, rdatasetheader_t *header,
* failed.
*/
if ((search->options & DNS_DBFIND_STALESTART) != 0) {
header->last_refresh_fail_ts = search->now;
atomic_store_release(
&header->last_refresh_fail_ts,
search->now);
} else if ((search->options &
DNS_DBFIND_STALEENABLED) != 0 &&
search->now <
(header->last_refresh_fail_ts +
(atomic_load_acquire(
&header->last_refresh_fail_ts) +
search->rbtdb->serve_stale_refresh))
{
/*