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From 34db150dae50363dd0f551175e160e9c238a251f Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhrozek@redhat.com>
Date: Wed, 18 Nov 2015 20:48:51 +0100
Subject: [PATCH 093/108] FO: Use tevent_req_defer_callback() when notifying
callers
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
If a fo_resolve_service callback would modify the server->common member
in any way, for example by dereferencing the server and lowering the
refcount to 0, which would free the common structure, then the next
iteration of fo_resolve_service_done would access memory that was
already gone.
Please see
https://tevent.samba.org/group__tevent__request.html#ga09373077d0b39e321a196a86bfebf280
for more details.
Reviewed-by: Pavel Březina <pbrezina@redhat.com>
(cherry picked from commit a92f68763a57b211a1bf6b80b6dd80c4a1aa2738)
(cherry picked from commit bbfc3a4294c6a70426171e080c27c15d9706bec7)
---
src/providers/fail_over.c | 15 +++++++++++--
src/tests/cmocka/test_fo_srv.c | 49 +++++++++++++++++++++++++++++++++++++++---
2 files changed, 59 insertions(+), 5 deletions(-)
diff --git a/src/providers/fail_over.c b/src/providers/fail_over.c
index b6f29a2a3e1d389560475ae05a4c9a846d817fdb..e945c9924597c7addeeb11090e1c1aee5596cb71 100644
--- a/src/providers/fail_over.c
+++ b/src/providers/fail_over.c
@@ -131,6 +131,7 @@ struct resolve_service_request {
struct server_common *server_common;
struct tevent_req *req;
+ struct tevent_context *ev;
};
struct status {
@@ -940,7 +941,9 @@ resolve_service_request_destructor(struct resolve_service_request *request)
}
static int
-set_lookup_hook(struct fo_server *server, struct tevent_req *req)
+set_lookup_hook(struct tevent_context *ev,
+ struct fo_server *server,
+ struct tevent_req *req)
{
struct resolve_service_request *request;
@@ -956,6 +959,7 @@ set_lookup_hook(struct fo_server *server, struct tevent_req *req)
talloc_free(request);
return ENOMEM;
}
+ request->ev = ev;
request->req = req;
DLIST_ADD(server->common->request_list, request);
talloc_set_destructor(request, resolve_service_request_destructor);
@@ -1142,7 +1146,7 @@ fo_resolve_service_server(struct tevent_req *req)
case SERVER_RESOLVING_NAME:
/* Name resolution is already under way. Just add ourselves into the
* waiting queue so we get notified after the operation is finished. */
- ret = set_lookup_hook(state->server, req);
+ ret = set_lookup_hook(state->ev, state->server, req);
if (ret != EOK) {
tevent_req_error(req, ret);
return true;
@@ -1194,6 +1198,13 @@ fo_resolve_service_done(struct tevent_req *subreq)
/* Take care of all requests for this server. */
while ((request = common->request_list) != NULL) {
DLIST_REMOVE(common->request_list, request);
+
+ /* If the request callback decresed refcount on the returned
+ * server, we would have crashed as common would not be valid
+ * anymore. Rather schedule the notify for next tev iteration
+ */
+ tevent_req_defer_callback(request->req, request->ev);
+
if (ret) {
tevent_req_error(request->req, ret);
} else {
diff --git a/src/tests/cmocka/test_fo_srv.c b/src/tests/cmocka/test_fo_srv.c
index 67f86fb17753bf90b88d007a6a1b309df830c152..a84ce4348d2e59aaab4fc9ac1bd4cfd853ff491d 100644
--- a/src/tests/cmocka/test_fo_srv.c
+++ b/src/tests/cmocka/test_fo_srv.c
@@ -575,10 +575,10 @@ static void test_fo_srv_before(struct tevent_req *req)
fo_set_server_status(test_ctx->srv, SERVER_WORKING);
/* Simulate changing the DNS environment. Change the host names */
- s1 = mock_ares_reply(test_ctx, "ldap2.sssd.com", 100, 2, 389);
+ s1 = mock_ares_reply(test_ctx, "ldap1.sssd.com", 100, 2, 389);
assert_non_null(s1);
- s2 = mock_ares_reply(test_ctx, "ldap3.sssd.com", 100, 1, 389);
+ s2 = mock_ares_reply(test_ctx, "ldap2.sssd.com", 100, 1, 389);
assert_non_null(s2);
s1->next = s2;
@@ -596,12 +596,17 @@ static void test_fo_srv_before(struct tevent_req *req)
tevent_req_set_callback(req, test_fo_srv_after, test_ctx);
}
+static void test_fo_srv_after2(struct tevent_req *req);
+
static void test_fo_srv_after(struct tevent_req *req)
{
struct test_fo_ctx *test_ctx = \
tevent_req_callback_data(req, struct test_fo_ctx);
struct fo_server *srv;
errno_t ret;
+ struct ares_srv_reply *s1;
+ struct ares_srv_reply *s2;
+ char *dns_domain;
ret = fo_resolve_service_recv(req, req, &srv);
talloc_zfree(req);
@@ -612,8 +617,46 @@ static void test_fo_srv_after(struct tevent_req *req)
*/
fo_set_server_status(test_ctx->srv, SERVER_WORKING);
+ sleep(test_ctx->ttl + 1);
+
/* Must be a different server now */
- check_server(test_ctx, srv, 389, "ldap3.sssd.com");
+ check_server(test_ctx, srv, 389, "ldap2.sssd.com");
+
+ /* Simulate changing the DNS environment. Change the host names */
+ s1 = mock_ares_reply(test_ctx, "ldap1.sssd.com", 100, 1, 389);
+ assert_non_null(s1);
+
+ s2 = mock_ares_reply(test_ctx, "ldap2.sssd.com", 100, 2, 389);
+ assert_non_null(s2);
+
+ s1->next = s2;
+
+ dns_domain = talloc_strdup(test_ctx, "sssd.com");
+ assert_non_null(dns_domain);
+
+ mock_srv_results(s1, test_ctx->ttl, dns_domain);
+ sleep(test_ctx->ttl + 1);
+
+ req = fo_resolve_service_send(test_ctx, test_ctx->ctx->ev,
+ test_ctx->resolv, test_ctx->fo_ctx,
+ test_ctx->fo_svc);
+ assert_non_null(req);
+ tevent_req_set_callback(req, test_fo_srv_after2, test_ctx);
+}
+
+static void test_fo_srv_after2(struct tevent_req *req)
+{
+ struct test_fo_ctx *test_ctx = \
+ tevent_req_callback_data(req, struct test_fo_ctx);
+ struct fo_server *srv;
+ errno_t ret;
+
+ ret = fo_resolve_service_recv(req, req, &srv);
+ talloc_zfree(req);
+ assert_int_equal(ret, ERR_OK);
+
+ /* Must be a different server now */
+ check_server(test_ctx, srv, 389, "ldap1.sssd.com");
test_ctx->ctx->error = ERR_OK;
test_ctx->ctx->done = true;
--
2.7.3
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