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diff --git a/lib/dns/resolver.c b/lib/dns/resolver.c
index a00c395db661d4df629b05d0b82031fd51d02c90..8d3df4ecc7519a62229e7ca8e987b4c8fcc29a55 100644 (file)
--- a/lib/dns/resolver.c
+++ b/lib/dns/resolver.c
@@ -6653,6 +6653,14 @@ resume_dslookup(isc_task_t *task, isc_event_t *event) {
        dns_rdataset_init(&nameservers);
 
        bucketnum = fctx->bucketnum;
+
+       /*
+        * Note: fevent->rdataset must be disassociated and
+        * isc_event_free(&event) be called before resuming
+        * processing of the 'fctx' to prevent use-after-free.
+        * 'fevent' is set to NULL so as to not have a dangling
+        * pointer.
+        */
        if (fevent->result == ISC_R_CANCELED) {
                if (dns_rdataset_isassociated(fevent->rdataset)) {
                        dns_rdataset_disassociate(fevent->rdataset);