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Restore more locking in the lib/dns/resolver.c code

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1. Restore locking in the fctx_decreference() code, because the insides of the
   function needs to be protected when fctx->references drops to 0.

2. Restore locking in the dns_resolver_attach() code, because two variables are
   accessed at the same time and there's slight chance of data race.
This commit is contained in:
Ondřej Surý 2019-07-22 08:45:23 -04:00
parent 317e36d47e
commit a4141fcf98
1 changed files with 5 additions and 1 deletions
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6
lib/dns/resolver.c
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@ -9384,7 +9384,9 @@ rctx_resend(respctx_t *rctx, dns_adbaddrinfo_t *addrinfo) {
}
fctx_done(fctx, result, __LINE__);
LOCK(&fctx->res->buckets[fctx->bucketnum].lock);
bucket_empty = fctx_decreference(fctx);
UNLOCK(&fctx->res->buckets[fctx->bucketnum].lock);
if (bucket_empty) {
empty_bucket(fctx->res);
}
@ -10278,8 +10280,10 @@ dns_resolver_attach(dns_resolver_t *source, dns_resolver_t **targetp) {
RRTRACE(source, "attach");
LOCK(&source->lock);
REQUIRE(!atomic_load_acquire(&source->exiting));
isc_refcount_increment(&source->references);
UNLOCK(&source->lock);
*targetp = source;
}
@ -10736,9 +10740,9 @@ dns_resolver_destroyfetch(dns_fetch_t **fetchp) {
RUNTIME_CHECK(event->fetch != fetch);
}
}
UNLOCK(&res->buckets[bucketnum].lock);
bucket_empty = fctx_decreference(fctx);
UNLOCK(&res->buckets[bucketnum].lock);
isc_mem_putanddetach(&fetch->mctx, fetch, sizeof(*fetch));
*fetchp = NULL;