mir/bind
2
0
Fork 0
mirror of https://gitlab.isc.org/isc-projects/bind9 synced 2025-08-31 14:35:26 +00:00
Code Issues Releases Wiki Activity

Fix deadlock in RPZ update code.

Browse Source 
In dns_rpz_update_from_db we call setup_update which creates the db
iterator and calls dns_dbiterator_first. This unpauses the iterator and
might cause db->tree_lock to be acquired. We then do isc_task_send(...)
on an event to do quantum_update, which (correctly) after each iteration
calls dns_dbiterator_pause, and re-isc_task_sends itself.

That's an obvious bug, as we're holding a lock over an async task send -
if a task requesting write (e.g. prune_tree) is scheduled on the same
workers queue as update_quantum but before it, it will wait for the
write lock indefinitely, resulting in a deadlock.

To fix it we have to pause dbiterator in setup_update.
This commit is contained in:
Witold Kręcicki
2019-04-04 22:05:25 +02:00
committed by Evan Hunt
parent b22a5b6fac
commit 06021b3529
2 changed files with 12 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
CHANGES
View File

@@ -1,3 +1,5 @@
5201. [bug] Fix a possible deadlock in RPZ update code. [GL #973]
5200. [placeholder]
5199. [placeholder]

10
lib/dns/rpz.c
View File

@@ -1732,6 +1732,16 @@ setup_update(dns_rpz_zone_t *rpz) {
goto cleanup;
}
result = dns_dbiterator_pause(rpz->updbit);
if (result != ISC_R_SUCCESS) {
isc_log_write(dns_lctx, DNS_LOGCATEGORY_GENERAL,
DNS_LOGMODULE_MASTER, ISC_LOG_ERROR,
"rpz: %s: failed to pause db iterator - %s",
domain, isc_result_totext(result));
goto cleanup;
}
cleanup:
if (result != ISC_R_SUCCESS) {
if (rpz->updbit != NULL)