bind9.18/bind-9.18-CVE-2026-11622.patch

From b2ae1983a8ef64e94b7374a7642587a6cd8a2144 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@sury.org>
Date: Tue, 23 Jun 2026 10:59:38 +0200
Subject: [PATCH] Make the dns_slabheaders in the cache reference counted

Instead of only reference counting the enclosing qpcnode, add the
reference counting directly to the slabheaders.  The reference is
incremented when an rdataset is bound to the header and decremented when
the rdataset is disassociated, so a stale slabheader can be removed from
the node's down chain as soon as its own reference count reaches zero,
instead of waiting for the whole qpcnode to become unreferenced.

Building on that, clean up the ancient headers eagerly: mark_ancient()
is made idempotent, releases the header's own (container) reference and
reaps the stale headers from the node's down chain as soon as their
references reach zero.  A header evicted over the per-name type limit is
expired only after the new rdataset has been bound, so the bind's
increment always precedes mark_ancient()'s decrement.

Because a header can now be reclaimed independently of its node, the
rdataset iterators must keep the header they are positioned on alive:
each iterator takes a reference on its current header and releases it
when it advances or is destroyed.  Iteration otherwise stays lazy and
re-reads the node on every step, so it still observes records added to
the node while the iterator is live, as zone signing requires.

The slab headers are shared with the zone databases, so the matching
increment is added to every bind path.  The noqname/closest proofs hand
out rdatasets backed by bare slabs that have no header, so they are
given a separate dns_rdataproof_rdatasetmethods that leaves the
reference count untouched.

(cherry picked from commit 2dabf117e1264fd13fb33096f87e78a039fd1c6c)

NOTE(fvorobev): TTL in the reclimit test was changed from 120 to 60, as
that is the value that is used in the zones for the test in bind
9.18.29.
---
 bin/tests/system/reclimit/tests.sh |  4 +-
 lib/dns/include/dns/rdataslab.h    |  1 +
 lib/dns/rbtdb.c                    | 77 +++++++++++++++++++++++++-----
 3 files changed, 69 insertions(+), 13 deletions(-)

diff --git a/bin/tests/system/reclimit/tests.sh b/bin/tests/system/reclimit/tests.sh
index 4d9105e..051b96c 100644
--- a/bin/tests/system/reclimit/tests.sh
+++ b/bin/tests/system/reclimit/tests.sh
@@ -331,13 +331,13 @@ echo_i "checking that NXDOMAIN names over the max-types-per-name limit don't get
 
 # Query for 10 NXDOMAIN types
 for ntype in $(seq 65270 65279); do
-  check_manytypes 1 manytypes.big "TYPE${ntype}" NOERROR big SOA 0 || ret=1
+  check_manytypes 1 manytypes.big "TYPE${ntype}" NOERROR big SOA 60 || ret=1
 done
 # Wait at least 1 second
 sleep 1
 # Query for 10 NXDOMAIN types again - these should not be cached
 for ntype in $(seq 65270 65279); do
-  check_manytypes 2 manytypes.big "TYPE${ntype}" NOERROR big SOA 0 || ret=1
+  check_manytypes 2 manytypes.big "TYPE${ntype}" NOERROR big SOA 60 || ret=1
 done
 
 if [ $ret -ne 0 ]; then echo_i "failed"; fi
diff --git a/lib/dns/include/dns/rdataslab.h b/lib/dns/include/dns/rdataslab.h
index 5729c00..6bd3b59 100644
--- a/lib/dns/include/dns/rdataslab.h
+++ b/lib/dns/include/dns/rdataslab.h
@@ -44,6 +44,7 @@
 #include <stdbool.h>
 
 #include <isc/lang.h>
+#include <isc/refcount.h>
 
 #include <dns/types.h>
 
diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
index 5c2f0b2..98f63ea 100644
--- a/lib/dns/rbtdb.c
+++ b/lib/dns/rbtdb.c
@@ -165,6 +165,7 @@ struct noqname {
 };
 
 typedef struct rdatasetheader {
+	isc_refcount_t references;
 	/*%
 	 * Locked by the owning node's lock.
 	 */
@@ -1452,6 +1453,7 @@ init_rdataset(dns_rbtdb_t *rbtdb, rdatasetheader_t *h) {
 	h->heap_index = 0;
 	atomic_init(&h->attributes, 0);
 	atomic_init(&h->last_refresh_fail_ts, 0);
+	isc_refcount_init(&h->references, 1);
 
 	STATIC_ASSERT((sizeof(h->attributes) == 2),
 		      "The .attributes field of rdatasetheader_t needs to be "
@@ -1564,6 +1566,9 @@ rollback_node(dns_rbtnode_t *node, rbtdb_serial_t serial) {
 	}
 }
 
+static void
+clean_stale_headers(dns_rbtdb_t *rbtdb, isc_mem_t *mctx, rdatasetheader_t *top);
+
 static void
 mark_header_ancient(dns_rbtdb_t *rbtdb, rdatasetheader_t *header) {
 	uint_least16_t attributes = atomic_load_acquire(&header->attributes);
@@ -1589,8 +1594,12 @@ mark_header_ancient(dns_rbtdb_t *rbtdb, rdatasetheader_t *header) {
 	update_rrsetstats(rbtdb, header->type, attributes, false);
 	header->node->dirty = 1;
 
+	isc_refcount_decrement(&header->references);
+
 	/* Increment the stats counter for the ancient RRtype. */
 	update_rrsetstats(rbtdb, header->type, newattributes, true);
+
+	clean_stale_headers(rbtdb, rbtdb->common.mctx, header);
 }
 
 static void
@@ -1626,12 +1635,19 @@ static void
 clean_stale_headers(dns_rbtdb_t *rbtdb, isc_mem_t *mctx,
 		    rdatasetheader_t *top) {
 	rdatasetheader_t *d, *down_next;
+	rdatasetheader_t *down_parent = top;
 
 	for (d = top->down; d != NULL; d = down_next) {
 		down_next = d->down;
-		free_rdataset(rbtdb, mctx, d);
+		d->next = down_parent;
+
+		if (isc_refcount_current(&d->references) == 0) {
+			free_rdataset(rbtdb, mctx, d);
+			down_parent->down = down_next;
+		} else {
+			down_parent = d;
+		}
 	}
-	top->down = NULL;
 }
 
 static void
@@ -1647,6 +1663,7 @@ clean_cache_node(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node) {
 	for (current = node->data; current != NULL; current = top_next) {
 		top_next = current->next;
 		clean_stale_headers(rbtdb, mctx, current);
+		INSIST(current->down == NULL);
 		/*
 		 * If current is nonexistent, ancient, or stale and
 		 * we are not keeping stale, we can clean it up.
@@ -3104,6 +3121,8 @@ bind_rdataset(dns_rbtdb_t *rbtdb, dns_rbtnode_t *node, rdatasetheader_t *header,
 		return;
 	}
 
+	isc_refcount_increment(&header->references);
+
 	new_reference(rbtdb, node, locktype);
 
 	INSIST(rdataset->methods == NULL); /* We must be disassociated. */
@@ -6293,6 +6312,7 @@ add32(dns_rbtdb_t *rbtdb, dns_rbtnode_t *rbtnode, const dns_name_t *nodename,
 	bool header_nx;
 	bool newheader_nx;
 	bool merge;
+	bool do_expireheader = false;
 	dns_rdatatype_t rdtype, covers;
 	rbtdb_rdatatype_t negtype, sigtype;
 	dns_trust_t trust;
@@ -6834,6 +6854,7 @@ find_header:
 			}
 
 			if (IS_CACHE(rbtdb) && overmaxtype(rbtdb, ntypes)) {
+				do_expireheader = true;
 				if (expireheader == NULL) {
 					expireheader = newheader;
 				}
@@ -6847,15 +6868,6 @@ find_header:
 					 */
 					expireheader = newheader;
 				}
-
-				set_ttl(rbtdb, expireheader, 0);
-				mark_header_ancient(rbtdb, expireheader);
-				/*
-				 * FIXME: In theory, we should mark the RRSIG
-				 * and the header at the same time, but there is
-				 * no direct link between those two header, so
-				 * we would have to check the whole list again.
-				 */
 			}
 		}
 	}
@@ -6879,6 +6891,15 @@ find_header:
 			      isc_rwlocktype_write, addedrdataset);
 	}
 
+	/*
+	 * We need to delay the expiration of the header until we are bound to
+	 * it to prevent decrement-then-increment on the header references.
+	 */
+	if (do_expireheader) {
+		set_ttl(rbtdb, expireheader, 0);
+		mark_header_ancient(rbtdb, expireheader);
+	}
+
 	return (ISC_R_SUCCESS);
 }
 
@@ -8658,6 +8679,12 @@ rdataset_disassociate(dns_rdataset_t *rdataset) {
 	dns_db_t *db = rdataset->private1;
 	dns_dbnode_t *node = rdataset->private2;
 
+	if (rdataset->methods == &rdataset_methods) {
+		rdatasetheader_t *header = rdataset->private3;
+		header--;
+		isc_refcount_decrement(&header->references);
+	}
+
 	detachnode(db, &node);
 }
 
@@ -8772,6 +8799,11 @@ rdataset_clone(dns_rdataset_t *source, dns_rdataset_t *target) {
 	dns_dbnode_t *cloned_node = NULL;
 
 	attachnode(db, node, &cloned_node);
+	if (source->methods == &rdataset_methods) {
+		rdatasetheader_t *header = source->private3;
+		header--;
+		isc_refcount_increment(&header->references);
+	}
 	INSIST(!ISC_LINK_LINKED(target, link));
 	*target = *source;
 	ISC_LINK_INIT(target, link);
@@ -8935,6 +8967,11 @@ rdatasetiter_destroy(dns_rdatasetiter_t **iteratorp) {
 
 	rbtiterator = (rbtdb_rdatasetiter_t *)(*iteratorp);
 
+	if (rbtiterator->current != NULL) {
+		isc_refcount_decrement(&rbtiterator->current->references);
+		rbtiterator->current = NULL;
+	}
+
 	if (rbtiterator->common.version != NULL) {
 		closeversion(rbtiterator->common.db,
 			     &rbtiterator->common.version, false);
@@ -9012,9 +9049,18 @@ rdatasetiter_first(dns_rdatasetiter_t *iterator) {
 		}
 	}
 
+	if (header != NULL) {
+		isc_refcount_increment0(&header->references);
+	}
+
 	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
 		    isc_rwlocktype_read);
 
+	if (rbtiterator->current != NULL) {
+		isc_refcount_decrement(&rbtiterator->current->references);
+		rbtiterator->current = NULL;
+	}
+
 	rbtiterator->current = header;
 
 	if (header == NULL) {
@@ -9106,9 +9152,18 @@ rdatasetiter_next(dns_rdatasetiter_t *iterator) {
 		}
 	}
 
+	if (header != NULL) {
+		isc_refcount_increment0(&header->references);
+	}
+
 	NODE_UNLOCK(&rbtdb->node_locks[rbtnode->locknum].lock,
 		    isc_rwlocktype_read);
 
+	if (rbtiterator->current != NULL) {
+		isc_refcount_decrement(&rbtiterator->current->references);
+		rbtiterator->current = NULL;
+	}
+
 	rbtiterator->current = header;
 
 	if (header == NULL) {
-- 
2.55.0