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prevent an infinite loop in fix_iterator()

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it was possible for fix_iterator() to get stuck in a loop while
trying to find the predecessor of a missing node. this has been
fixed and a regression test has been added.
This commit is contained in:
Evan Hunt 2023-12-20 00:32:57 -08:00
parent 84f79cd164
commit ea9a8cb392
2 changed files with 54 additions and 2 deletions
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13
lib/dns/qp.c
View file

@ -2115,6 +2115,17 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpnode_t *start,
return (leaf);
}
/*
* Special case: if the search key differs even before the root
* key offset, it means the name desired either precedes or
* follows the entire range of names in the database, and
* popping up the stack won't help us, so just move the
* iterator one step back from the origin and return.
*/
if (to < branch_key_offset(iter->stack[0])) {
dns_qpiter_init(qp, iter);
return (prevleaf(iter));
}
/*
* As long as the branch offset point is after the point where the
* search key differs, we need to branch up and find a better leaf
@ -2128,8 +2139,6 @@ fix_iterator(dns_qpreader_t *qp, dns_qpiter_t *iter, dns_qpnode_t *start,
* go to the parent branch and iterate back to the
* predecessor from that point.
*/
iter->stack[iter->sp] = NULL;
iter->sp--;
n = prevleaf(iter);
leaf = n;
} else {

43
tests/dns/qp_test.c
View file

@ -755,6 +755,48 @@ ISC_RUN_TEST_IMPL(predecessors) {
dns_qp_destroy(&qp);
}
/*
* this is a regression test for an infinite loop that could
* previously occur in fix_iterator()
*/
ISC_RUN_TEST_IMPL(fixiterator) {
dns_qp_t *qp = NULL;
const char insert[][32] = { "dynamic.",
"a.dynamic.",
"aaaa.dynamic.",
"cdnskey.dynamic.",
"cds.dynamic.",
"cname.dynamic.",
"dname.dynamic.",
"dnskey.dynamic.",
"ds.dynamic.",
"mx.dynamic.",
"ns.dynamic.",
"nsec.dynamic.",
"private-cdnskey.dynamic.",
"private-dnskey.dynamic.",
"rrsig.dynamic.",
"txt.dynamic.",
"" };
int i = 0;
dns_qp_create(mctx, &string_methods, NULL, &qp);
while (insert[i][0] != '\0') {
insert_str(qp, insert[i++]);
}
static struct check_predecessors check1[] = {
{ "newtext.dynamic.", "mx.dynamic.", DNS_R_PARTIALMATCH, 6 },
{ "absent.", "txt.dynamic.", ISC_R_NOTFOUND, 0 },
{ "nonexistent.", "txt.dynamic.", ISC_R_NOTFOUND, 0 },
{ NULL, NULL, 0, 0 }
};
check_predecessors(qp, check1);
dns_qp_destroy(&qp);
}
ISC_TEST_LIST_START
ISC_TEST_ENTRY(qpkey_name)
ISC_TEST_ENTRY(qpkey_sort)
@ -762,6 +804,7 @@ ISC_TEST_ENTRY(qpiter)
ISC_TEST_ENTRY(partialmatch)
ISC_TEST_ENTRY(qpchain)
ISC_TEST_ENTRY(predecessors)
ISC_TEST_ENTRY(fixiterator)
ISC_TEST_LIST_END
ISC_TEST_MAIN