From: Alex Rousskov <rousskov@measurement-factory.com>
Date: Thu, 11 Jul 2024 20:04:06 +0000 (+0000)
Subject: Be more careful when updating nameservers global (#1862)
X-Git-Tag: SQUID_6_11~9
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f8e9ce2eef1c5c7739ce578ebb21985bab049327;p=thirdparty%2Fsquid.git

Be more careful when updating nameservers global (#1862)

Due to I/O delays and timeouts, DNS nsvc objects may be deleted after
the `nameservers` global pointing to them was cleared and then populated
with new ns objects. Thus, nsvc destructor should check that nsvc and
`nameservers` states are still in sync before manipulating the latter.

DNS code should use similar validation in a few other places, but they
are all about read-only debugging that requires a rather noisy cleanup.
---

diff --git a/src/dns_internal.cc b/src/dns_internal.cc
index 5aa311ae4b..b60854b090 100644
--- a/src/dns_internal.cc
+++ b/src/dns_internal.cc
@@ -885,7 +885,9 @@ nsvc::~nsvc()
 {
     delete queue;
     delete msg;
-    if (ns < nameservers.size()) // XXX: idnsShutdownAndFreeState may have freed nameservers[]
+    // we may outlive nameservers version that was pointing to us because
+    // reconfigurations repopulate nameservers
+    if (ns < nameservers.size() && nameservers[ns].vc == this)
         nameservers[ns].vc = nullptr;
 }