Bug 14676 - Error backing up offline domain with lmdb >= 0.9.26
Summary: Error backing up offline domain with lmdb >= 0.9.26
Alias: None
Product: Samba 4.1 and newer
Classification: Unclassified
Component: Tools (show other bugs)
Version: 4.14.0
Hardware: All Linux
: P5 normal (vote)
Target Milestone: ---
Assignee: Jo Sutton
QA Contact: Samba QA Contact
Depends on:
Reported: 2021-03-21 22:55 UTC by Jo Sutton
Modified: 2022-09-13 20:42 UTC (History)
3 users (show)

See Also:

patch for 4.13 (10.65 KB, patch)
2021-03-25 00:25 UTC, Jo Sutton
abartlet: review+
patch for 4.14 (10.65 KB, patch)
2021-03-25 00:39 UTC, Jo Sutton
abartlet: review+

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Description Jo Sutton 2021-03-21 22:55:36 UTC
From https://gitlab.com/samba-team/samba/-/merge_requests/1854/diffs?commit_id=86fb7c69edd0a0bd8815b38daa4960a62c93a5c3:

"The LMDB change "ITS#9278 fix robust mutex cleanup for FreeBSD" released
in version 0.9.26 makes samba-tool domain backup offline to fail with
the following error:

Failed to connect to 'mdb:///tmp/foo/private/sam.ldb.d/CN=CONFIGURATION,DC=FOO,DC=EXAMPLE,DC=COM.ldb' with backend 'mdb': Unable to load ltdb cache records for backend 'ldb_mdb backend'
module samba_dsdb initialization failed : Operations error
Unable to load modules for /tmp/foo/private/sam.ldb.bak-offline: Unable to load ltdb cache records for backend 'ldb_mdb backend'
ERROR(ldb): uncaught exception - Unable to load ltdb cache records for backend 'ldb_mdb backend'
  File "/usr/local/samba/lib64/python3.6/site-packages/samba/netcmd/__init__.py", line 186, in _run
    return self.run(*args, **kwargs)
  File "/usr/local/samba/lib64/python3.6/site-packages/samba/netcmd/domain_backup.py", line 1147, in run
    session_info=system_session(), lp=lp)
  File "/usr/local/samba/lib64/python3.6/site-packages/samba/samdb.py", line 72, in __init__
  File "/usr/local/samba/lib64/python3.6/site-packages/samba/__init__.py", line 114, in __init__
    self.connect(url, flags, options)
  File "/usr/local/samba/lib64/python3.6/site-packages/samba/samdb.py", line 87, in connect

The error occurs opening the backed ldb to write the backup date and the
next SID, a call to pthread_mutex_lock in mdb_txn_renew0 (frame 8) returns

  #0  0x00007ff63c2f1bea in wait4 () from /lib64/libc.so.6
  #1  0x00007ff63c26f3a3 in do_system () from /lib64/libc.so.6
  #2  0x00007ff63bc71e94 in smb_panic_default (why=0x7ffed481b7d0 "Signal 6: Aborted") at ../../lib/util/fault.c:153
  #3  0x00007ff63bc72168 in smb_panic (why=0x7ffed481b7d0 "Signal 6: Aborted") at ../../lib/util/fault.c:200
  #4  0x00007ff63bc71c82 in fault_report (sig=6) at ../../lib/util/fault.c:81
  #5  0x00007ff63bc71c97 in sig_fault (sig=6) at ../../lib/util/fault.c:92
  #6  <signal handler called>
  #7  0x00007ff63c2178b5 in raise () from /lib64/libpthread.so.0
  #8  0x00007ff637602e65 in mdb_txn_renew0 (txn=txn@entry=0x55d6f97fb800) at mdb.c:2710
  #9  0x00007ff637603ae8 in mdb_txn_begin (env=0x55d6f85dfa80, parent=0x0, flags=131072, ret=0x55d6f89c0928)
      at mdb.c:2912
  #10 0x00007ff6376236cc in lmdb_lock_read (module=0x55d6f8c5f4b0) at ../../lib/ldb/ldb_mdb/ldb_mdb.c:585
  #11 0x00007ff637641de6 in ldb_kv_cache_load (module=0x55d6f8c5f4b0) at ../../lib/ldb/ldb_key_value/ldb_kv_cache.c:450
  #12 0x00007ff637638792 in ldb_kv_init_store (ldb_kv=0x55d6f8af2a80, name=0x7ff637625675 "ldb_mdb backend",
      ldb=0x55d6f8cd22b0, options=0x0, _module=0x7ffed481c248) at ../../lib/ldb/ldb_key_value/ldb_kv.c:2166
  #13 0x00007ff6376247ba in lmdb_connect (ldb=0x55d6f8cd22b0,
      url=0x55d6f85d41f0 "mdb:///tmp/foo/private/sam.ldb.d/CN=CONFIGURATION,DC=FOO,DC=EXAMPLE,DC=COM.ldb", flags=64,
      options=0x0, _module=0x7ffed481c248) at ../../lib/ldb/ldb_mdb/ldb_mdb.c:1143
  #14 0x00007ff63bd94d2f in ldb_module_connect_backend (ldb=0x55d6f8cd22b0,
      url=0x55d6f85d41f0 "mdb:///tmp/foo/private/sam.ldb.d/CN=CONFIGURATION,DC=FOO,DC=EXAMPLE,DC=COM.ldb",
      options=0x0, backend_module=0x7ffed481c248) at ../../lib/ldb/common/ldb_modules.c:221
  #15 0x00007ff6375a4baf in new_partition_from_dn (ldb=0x55d6f8cd22b0, data=0x55d6f858bed0, mem_ctx=0x55d6f8a03cd0,
      dn=0x55d6f9865450, filename=0x55d6f860b6da "sam.ldb.d/CN=CONFIGURATION,DC=FOO,DC=EXAMPLE,DC=COM.ldb",
      backend_db_store=0x55d6f9d378e0 "mdb", partition=0x7ffed481c308)
      at ../../source4/dsdb/samdb/ldb_modules/partition_init.c:257
  #16 0x00007ff6375a57b9 in partition_reload_if_required (module=0x55d6f8972d10, data=0x55d6f858bed0, parent=0x0)
      at ../../source4/dsdb/samdb/ldb_modules/partition_init.c:513
  #17 0x00007ff6375a3b04 in partition_read_lock (module=0x55d6f8972d10)
      at ../../source4/dsdb/samdb/ldb_modules/partition.c:1492
  #18 0x00007ff63bd9631e in ldb_next_read_lock (module=0x55d6f8972d10) at ../../lib/ldb/common/ldb_modules.c:662
  #19 0x00007ff637484857 in schema_read_lock (module=0x55d6f9377e40)
      at ../../source4/dsdb/samdb/ldb_modules/schema_load.c:614
  #20 0x00007ff63bd9631e in ldb_next_read_lock (module=0x55d6f9377e40) at ../../lib/ldb/common/ldb_modules.c:662
  #21 0x00007ff6374b5402 in samba_dsdb_init (module=0x55d6f91c3cd0)
      at ../../source4/dsdb/samdb/ldb_modules/samba_dsdb.c:483
  #22 0x00007ff63bd95283 in ldb_module_init_chain (ldb=0x55d6f8cd22b0, module=0x55d6f91c3cd0)
      at ../../lib/ldb/common/ldb_modules.c:363
  #23 0x00007ff63bd95645 in ldb_load_modules (ldb=0x55d6f8cd22b0, options=0x0)
      at ../../lib/ldb/common/ldb_modules.c:445
  #24 0x00007ff63bd90663 in ldb_connect (ldb=0x55d6f8cd22b0,
      url=0x7ff6377d98f8 "/tmp/foo/private/sam.ldb.bak-offline", flags=64, options=0x0)
      at ../../lib/ldb/common/ldb.c:274
  #25 0x00007ff63bddb32f in py_ldb_connect (self=0x7ff63778afc0, args=(), Python Exception <class 'gdb.error'> There is no member named ma_keys.:
  kwargs=) at ../../lib/ldb/pyldb.c:1235

Deleting the previous samdb instance by setting it to None before opening the
backed ldb workaround the problem until we find the real problem here."
Comment 1 Jo Sutton 2021-03-21 23:24:26 UTC
Opening the backed up database to insert the backup markers unnecessarily opens the backend database files, which may already be open in the same process. By specifying that no modules should be loaded when opening the main database, we can avoid opening any additional files.
Comment 2 Samba QA Contact 2021-03-24 03:14:06 UTC
This bug was referenced in samba master:

Comment 3 Jo Sutton 2021-03-25 00:25:45 UTC
Created attachment 16568 [details]
patch for 4.13
Comment 4 Jo Sutton 2021-03-25 00:39:08 UTC
Created attachment 16569 [details]
patch for 4.14
Comment 5 Samba QA Contact 2021-08-24 13:23:18 UTC
This bug was referenced in samba master:

Comment 6 Samba QA Contact 2021-09-08 13:55:14 UTC
This bug was referenced in samba v4-15-test:

Comment 7 Samba QA Contact 2021-09-09 06:55:55 UTC
This bug was referenced in samba v4-15-stable (Release samba-4.15.0rc6):

Comment 8 Jo Sutton 2022-08-26 02:06:12 UTC
Fixed in Samba 4.15 and above, closing.