just for comparison: here the stacktrace on a older bind9 (9.19.21-1+b1) with
the same samba dlz module when set a breakpoint on the line that causes an
issue on newer bind9 (and stepped into "free"):
#0 __GI___libc_free (mem=0x55a6b4273020) at ./malloc/malloc.c:3356
#1 0x00007f7bead76155 in schema_metadata_get_uint64 (key=0x7f7bead77dcb
"SCHEMA_SEQ_NUM", default_value=0, value=<synthetic pointer>,
data=0x55a6b42f1e40)
at source4/dsdb/samdb/ldb_modules/schema_load.c:187
#2 dsdb_schema_refresh (module=module@entry=0x55a6b42f4840, ev=<optimized
out>, schema=schema@entry=0x0, is_global_schema=is_global_schema@entry=true) at
source4/dsdb/samdb/ldb_modules/schema_load.c:246
#3 0x00007f7bebde082b in dsdb_get_schema (ldb=0x55a6b42913b0,
reference_ctx=0x55a6b43272f0) at source4/dsdb/schema/schema_set.c:896
#4 0x00007f7bead75d5c in schema_load (need_write=0x55a6b42f1e6c,
module=<optimized out>, ldb=0x55a6b42913b0) at
source4/dsdb/samdb/ldb_modules/schema_load.c:443
#5 schema_load_init (module=<optimized out>) at
source4/dsdb/samdb/ldb_modules/schema_load.c:489
#6 0x00007f7bed6a42c2 in ldb_module_init_chain () from
/lib/x86_64-linux-gnu/libldb.so.2
#7 0x00007f7bed6a42c2 in ldb_module_init_chain () from
/lib/x86_64-linux-gnu/libldb.so.2
#8 0x00007f7beadd1dd4 in rootdse_init (module=0x55a6b42f4a70) at
source4/dsdb/samdb/ldb_modules/rootdse.c:1013
#9 0x00007f7bed6a42c2 in ldb_module_init_chain () from
/lib/x86_64-linux-gnu/libldb.so.2
#10 0x00007f7beada5f13 in samba_dsdb_init (module=0x55a6b42e6870) at
source4/dsdb/samdb/ldb_modules/samba_dsdb.c:491
#11 0x00007f7bed6a42c2 in ldb_module_init_chain () from
/lib/x86_64-linux-gnu/libldb.so.2
#12 0x00007f7bed6a43ac in ldb_load_modules () from
/lib/x86_64-linux-gnu/libldb.so.2
#13 0x00007f7bed6a32be in ldb_connect () from /lib/x86_64-linux-gnu/libldb.so.2
#14 0x00007f7bebddb435 in samba_ldb_connect (ldb=ldb@entry=0x55a6b42913b0,
lp_ctx=lp_ctx@entry=0x55a6b428de20, url=url@entry=0x55a6b429cc50
"/var/lib/samba/bind-dns/dns/sam.ldb", flags=flags@entry=64)
at lib/ldb-samba/ldb_wrap.c:230
#15 0x00007f7bed374678 in samdb_connect_url
(mem_ctx=mem_ctx@entry=0x55a6b428c6a0, ev_ctx=0x55a6b4293720,
lp_ctx=0x55a6b428de20, session_info=0x55a6b4245150, flags=64, flags@entry=0,
url=url@entry=0x55a6b429cc50 "/var/lib/samba/bind-dns/dns/sam.ldb",
remote_address=0x0, ldb_ret=0x55a6b428c6b0, errstring=0x7ffe147b56f0) at
source4/dsdb/samdb/samdb.c:96
#16 0x00007f7bf015ba6e in dlz_create (dlzname=<optimized out>, argc=1,
argv=0x7f7bedcd2308, dbdata=0x7f7bedd60a08) at
source4/dns_server/dlz_bind9.c:741
#17 0x000055a6b23f9678 in ?? ()
#18 0x00007f7bf173561a in ?? () from
/lib/x86_64-linux-gnu/libdns-9.19.21-1+b1-Debian.so
#19 0x00007f7bf16577d5 in dns_dlzcreate () from
/lib/x86_64-linux-gnu/libdns-9.19.21-1+b1-Debian.so
#20 0x000055a6b240d52a in ?? ()
#21 0x000055a6b241e790 in ?? ()
#22 0x000055a6b241ee58 in ?? ()
#23 0x00007f7bf199a7d7 in isc.async_cb () from
/lib/x86_64-linux-gnu/libisc-9.19.21-1+b1-Debian.so
#24 0x00007f7bf1856d33 in ?? () from /lib/x86_64-linux-gnu/libuv.so.1
#25 0x00007f7bf186aa72 in ?? () from /lib/x86_64-linux-gnu/libuv.so.1
#26 0x00007f7bf18579f8 in uv_run () from /lib/x86_64-linux-gnu/libuv.so.1
#27 0x00007f7bf19ad5e0 in ?? () from
/lib/x86_64-linux-gnu/libisc-9.19.21-1+b1-Debian.so
#28 0x000055a6b23ee928 in main ()
the thing that looks different is that mem is not <optimized out>. The rest
looks quite similar
