tldap: avoid a use after free crash

tldap: avoid a use after free crash

I saw the following crash in tldap in the winbindd idmap child on a
member server after messing with the LDAP server on the DC:

0  0x00007f77ea9a307a in __GI___waitpid (pid=9815, stat_loc=stat_loc@entry=0x7ffe77569eb0, options=options@entry=0) at ../sysdeps/unix/sysv/linux/waitpid.c:29
1  0x00007f77ea91bfbb in do_system (line=<optimized out>) at ../sysdeps/posix/system.c:148
2  0x00007f77edd8c24b in smb_panic_s3 (why=0x7f77f08e6e88 "Bad talloc magic value - access after free") at ../source3/lib/util.c:828
3  0x00007f77f15afe85 in smb_panic (why=0x7f77f08e6e88 "Bad talloc magic value - access after free") at ../lib/util/fault.c:170
4  0x00007f77f08e2678 in talloc_abort (reason=0x7f77f08e6e88 "Bad talloc magic value - access after free") at ../lib/talloc/talloc.c:472
5  0x00007f77f08e268b in talloc_abort_access_after_free () at ../lib/talloc/talloc.c:477
6  0x00007f77f08e2710 in talloc_chunk_from_ptr (ptr=0x55da7605a020) at ../lib/talloc/talloc.c:494
7  0x00007f77f08e4a19 in _talloc_free (ptr=0x55da7605a020, location=0x7f77e181474d "../source3/lib/tldap.c:1918") at ../lib/talloc/talloc.c:1716
8  0x00007f77e180b65c in tldap_search_all_done (subreq=0x55da7605a020) at ../source3/lib/tldap.c:1918
9  0x00007f77f0af0fd0 in _tevent_req_notify_callback (req=0x55da7605a020, location=0x7f77e1813e50 "../source3/lib/tldap.c:47") at ../lib/tevent/tevent_req.c:125
10 0x00007f77f0af10a5 in tevent_req_finish (req=0x55da7605a020, state=TEVENT_REQ_USER_ERROR, location=0x7f77e1813e50 "../source3/lib/tldap.c:47") at ../lib/tevent/tevent_req.c:162
11 0x00007f77f0af1113 in _tevent_req_error (req=0x55da7605a020, error=9780923860630110289, location=0x7f77e1813e50 "../source3/lib/tldap.c:47") at ../lib/tevent/tevent_req.c:180
12 0x00007f77e180781a in tevent_req_ldap_error (req=0x55da7605a020, rc=...) at ../source3/lib/tldap.c:47
13 0x00007f77e180b2c4 in tldap_search_done (subreq=0x55da76058280) at ../source3/lib/tldap.c:1813
14 0x00007f77f0af0fd0 in _tevent_req_notify_callback (req=0x55da76058280, location=0x7f77e1813e50 "../source3/lib/tldap.c:47") at ../lib/tevent/tevent_req.c:125
15 0x00007f77f0af10a5 in tevent_req_finish (req=0x55da76058280, state=TEVENT_REQ_USER_ERROR, location=0x7f77e1813e50 "../source3/lib/tldap.c:47") at ../lib/tevent/tevent_req.c:162
16 0x00007f77f0af11cd in tevent_req_trigger (ev=0x55da760526c0, im=0x55da76058360, private_data=0x55da76058280) at ../lib/tevent/tevent_req.c:219
17 0x00007f77f0af0378 in tevent_common_loop_immediate (ev=0x55da760526c0) at ../lib/tevent/tevent_immediate.c:135
18 0x00007f77f0af8b8f in epoll_event_loop_once (ev=0x55da760526c0, location=0x7f77f0af92b0 "../lib/tevent/tevent_req.c:269") at ../lib/tevent/tevent_epoll.c:911
19 0x00007f77f0af5925 in std_event_loop_once (ev=0x55da760526c0, location=0x7f77f0af92b0 "../lib/tevent/tevent_req.c:269") at ../lib/tevent/tevent_standard.c:114
20 0x00007f77f0aef201 in _tevent_loop_once (ev=0x55da760526c0, location=0x7f77f0af92b0 "../lib/tevent/tevent_req.c:269") at ../lib/tevent/tevent.c:725
21 0x00007f77f0af1361 in tevent_req_poll (req=0x55da7605eed0, ev=0x55da760526c0) at ../lib/tevent/tevent_req.c:269
22 0x00007f77e180fec9 in tldap_gensec_bind (ctx=0x55da76051ec0, creds=0x55da76052250, target_service=0x7f77e18164b3 "ldap", target_hostname=0x55da7605d182 "dc1.sdom1.site", target_principal=0x0, lp_ctx=0x55da76052180, gensec_features=6) at ../source3/lib/tldap_gensec_bind.c:358
23 0x00007f77e1810d21 in idmap_ad_get_tldap_ctx (mem_ctx=0x55da76050510, domname=0x55da76051d50 "sdom1", pld=0x55da76050518) at ../source3/winbindd/idmap_ad.c:326
24 0x00007f77e1811056 in idmap_ad_context_create (mem_ctx=0x55da76059c00, dom=0x55da76059c00, domname=0x55da76051d50 "sdom1", pctx=0x7ffe7756a5f8) at ../source3/winbindd/idmap_ad.c:374
25 0x00007f77e18119c0 in idmap_ad_get_context (dom=0x55da76059c00, pctx=0x7ffe7756a640) at ../source3/winbindd/idmap_ad.c:554
26 0x00007f77e181275b in idmap_ad_sids_to_unixids (dom=0x55da76059c00, ids=0x55da760518a0) at ../source3/winbindd/idmap_ad.c:784
27 0x00007f77e1813217 in idmap_ad_sids_to_unixids_retry (dom=0x55da76059c00, ids=0x55da760518a0) at ../source3/winbindd/idmap_ad.c:947
28 0x000055da7459ce05 in _wbint_Sids2UnixIDs (p=0x7ffe7756a870, r=0x55da76050860) at ../source3/winbindd/winbindd_dual_srv.c:202
29 0x000055da7460aa5e in api_wbint_Sids2UnixIDs (p=0x7ffe7756a870) at default/librpc/gen_ndr/srv_winbind.c:391
30 0x000055da7459c7f4 in winbindd_dual_ndrcmd (domain=0x0, state=0x7ffe7756abb8) at ../source3/winbindd/winbindd_dual_ndr.c:369
31 0x000055da7459828c in child_process_request (child=0x55da74874bc0 <static_idmap_child>, state=0x7ffe7756abb8) at ../source3/winbindd/winbindd_dual.c:666
32 0x000055da7459ae58 in child_handler (ev=0x55da7602c2b0, fde=0x55da7603f8a0, flags=1, private_data=0x7ffe7756abb0) at ../source3/winbindd/winbindd_dual.c:1567
33 0x00007f77f0af85f1 in epoll_event_loop (epoll_ev=0x55da76048b00, tvalp=0x7ffe7756aab0) at ../lib/tevent/tevent_epoll.c:728
34 0x00007f77f0af8c29 in epoll_event_loop_once (ev=0x55da7602c2b0, location=0x55da74628b08 "../source3/winbindd/winbindd_dual.c:1766") at ../lib/tevent/tevent_epoll.c:930
35 0x00007f77f0af5925 in std_event_loop_once (ev=0x55da7602c2b0, location=0x55da74628b08 "../source3/winbindd/winbindd_dual.c:1766") at ../lib/tevent/tevent_standard.c:114
36 0x00007f77f0aef201 in _tevent_loop_once (ev=0x55da7602c2b0, location=0x55da74628b08 "../source3/winbindd/winbindd_dual.c:1766") at ../lib/tevent/tevent.c:725
37 0x000055da7459b9e9 in fork_domain_child (child=0x55da74874bc0 <static_idmap_child>) at ../source3/winbindd/winbindd_dual.c:1766
38 0x000055da74596e96 in wb_child_request_waited (subreq=0x0) at ../source3/winbindd/winbindd_dual.c:188
39 0x00007f77f0af0fd0 in _tevent_req_notify_callback (req=0x55da7604f820, location=0x7f77f0af90f8 "../lib/tevent/tevent_queue.c:355") at ../lib/tevent/tevent_req.c:125
40 0x00007f77f0af10a5 in tevent_req_finish (req=0x55da7604f820, state=TEVENT_REQ_DONE, location=0x7f77f0af90f8 "../lib/tevent/tevent_queue.c:355") at ../lib/tevent/tevent_req.c:162
41 0x00007f77f0af10cd in _tevent_req_done (req=0x55da7604f820, location=0x7f77f0af90f8 "../lib/tevent/tevent_queue.c:355") at ../lib/tevent/tevent_req.c:168
42 0x00007f77f0af0cc1 in tevent_queue_wait_trigger (req=0x55da7604f820, private_data=0x0) at ../lib/tevent/tevent_queue.c:355
43 0x00007f77f0af06f2 in tevent_queue_immediate_trigger (ev=0x55da7602c2b0, im=0x55da760466a0, private_data=0x55da76046580) at ../lib/tevent/tevent_queue.c:149
44 0x00007f77f0af0378 in tevent_common_loop_immediate (ev=0x55da7602c2b0) at ../lib/tevent/tevent_immediate.c:135
45 0x00007f77f0af8b8f in epoll_event_loop_once (ev=0x55da7602c2b0, location=0x55da74612630 "../source3/winbindd/winbindd.c:1803") at ../lib/tevent/tevent_epoll.c:911
46 0x00007f77f0af5925 in std_event_loop_once (ev=0x55da7602c2b0, location=0x55da74612630 "../source3/winbindd/winbindd.c:1803") at ../lib/tevent/tevent_standard.c:114
47 0x00007f77f0aef201 in _tevent_loop_once (ev=0x55da7602c2b0, location=0x55da74612630 "../source3/winbindd/winbindd.c:1803") at ../lib/tevent/tevent.c:725
48 0x000055da74561431 in main (argc=2, argv=0x7ffe7756c968) at ../source3/winbindd/winbindd.c:1803

subreq is a child of the state of req which will already be free by the
callback of req.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13776

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
(cherry picked from commit 9465292d4109f710f8fcd141a076f5c8278577bc)