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BUG/MEDIUM: resolvers: Remove aborted resolutions from query_ids tree

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To avoid any UAF when a resolution is released, a mechanism was added to
abort a resolution and delayed the released at the end of the current
execution path. This mechanism depends on an hard assumption: Any reference
on an aborted resolution must be removed. So, when a resolution is aborted,
it is removed from the resolver lists and inserted into a death row list.

However, a resolution may still be referenced in the query_ids tree. It is
the tree containing all resolutions with a pending request. Because aborted
resolutions are released outside the resolvers lock, it is possible to
release a resolution on a side while a query ansswer is received and
processed on another one. Thus, it is still possible to have a UAF because
of this bug.

To fix the issue, when a resolution is aborted, it is removed from any list,
but it is also removed from the query_ids tree.

This patch should solve the issue #1862 and may be related to #1875. It must
be backported as far as 2.2.

(cherry picked from commit eaabf060312f6aad1c0c195ad33e5ea612acc47a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
This commit is contained in:
Christopher Faulet 2022-09-27 10:43:24 +02:00
parent b93ce2eec3
commit 4d4abc49b3
1 changed files with 5 additions and 0 deletions
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5
src/resolvers.c
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@ -594,6 +594,11 @@ static void enter_resolver_code()
/* Add a resolution to the death_row. */
static void abort_resolution(struct resolv_resolution *res)
{
/* Remove the resolution from query_ids tree and from any resolvers list */
eb32_delete(&res->qid);
res->query_id = 0;
res->qid.key = 0;
LIST_DEL_INIT(&res->list);
LIST_APPEND(&death_row, &res->list);
}