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From c0134bbea5573b1911d204b28eb8c71351a0173f Mon Sep 17 00:00:00 2001
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From: Mark Andrews <marka@isc.org>
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Date: Fri, 18 Dec 2020 13:31:07 +1100
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Subject: [PATCH] Inactive incorrectly incremented
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It is possible to have two threads destroying an rbtdb at the same
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time when detachnode() executes and removes the last reference to
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a node between exiting being set to true for the node and testing
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if the references are zero in maybe_free_rbtdb(). Move NODE_UNLOCK()
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to after checking if references is zero to prevent detachnode()
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changing the reference count too early.
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(cherry picked from commit 859d2fdad6d1c6ff20083a4c463a929cbeb26438)
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(cherry picked from commit 25150c15e7cfa73289f04470e2e699ebb7c28fef)
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---
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lib/dns/rbtdb.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/lib/dns/rbtdb.c b/lib/dns/rbtdb.c
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index 29778d79a5..b01b44c4c7 100644
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--- a/lib/dns/rbtdb.c
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+++ b/lib/dns/rbtdb.c
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@@ -1399,11 +1399,11 @@ maybe_free_rbtdb(dns_rbtdb_t *rbtdb) {
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for (i = 0; i < rbtdb->node_lock_count; i++) {
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NODE_LOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_write);
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rbtdb->node_locks[i].exiting = ISC_TRUE;
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- NODE_UNLOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_write);
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if (isc_refcount_current(&rbtdb->node_locks[i].references)
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== 0) {
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inactive++;
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}
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+ NODE_UNLOCK(&rbtdb->node_locks[i].lock, isc_rwlocktype_write);
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}
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if (inactive != 0) {
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--
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2.26.3
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