sudo: always use srv_opts from id context

Prior this patch, we remember id_ctx->srv_opts in sudo request to switch
the latest usn values. This works fine most of the time but it may cause
a crash.

If we have two concurrent sudo refresh and one of these fails, it causes
failover to try the next server and possibly replacing the old srv_opts
with new one and it causes an access after free in the other refresh.

Resolves:
https://pagure.io/SSSD/sssd/issue/3562

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

src/providers/ldap/sdap_async_sudo.c

@@ -279,7 +279,6 @@ static char *sdap_sudo_get_filter(TALLOC_CTX *mem_ctx,
 struct sdap_sudo_refresh_state {
     struct sdap_sudo_ctx *sudo_ctx;
     struct tevent_context *ev;
-    struct sdap_server_opts *srv_opts;
     struct sdap_options *opts;
     struct sdap_id_op *sdap_op;
     struct sysdb_ctx *sysdb;
@@ -405,9 +404,6 @@ static void sdap_sudo_refresh_connect_done(struct tevent_req *subreq)
 
     DEBUG(SSSDBG_TRACE_FUNC, "SUDO LDAP connection successful\n");
 
-    /* Obtain srv_opts here in case of first connection. */
-    state->srv_opts = state->sudo_ctx->id_ctx->srv_opts;
-
     /* Renew host information if needed. */
     if (state->sudo_ctx->run_hostinfo) {
         subreq = sdap_sudo_get_hostinfo_send(state, state->opts,
@@ -586,7 +582,6 @@ static void sdap_sudo_refresh_done(struct tevent_req *subreq)
         goto done;
     }
 
-
     /* start transaction */
     ret = sysdb_transaction_start(state->sysdb);
     if (ret != EOK) {
@@ -621,7 +616,7 @@ static void sdap_sudo_refresh_done(struct tevent_req *subreq)
     /* remember new usn */
     ret = sysdb_get_highest_usn(state, rules, rules_count, &usn);
     if (ret == EOK) {
-        sdap_sudo_set_usn(state->srv_opts, usn);
+        sdap_sudo_set_usn(state->sudo_ctx->id_ctx->srv_opts, usn);
     } else {
         DEBUG(SSSDBG_MINOR_FAILURE, "Unable to get highest USN [%d]: %s\n",
               ret, sss_strerror(ret));