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mdssvc: Do an early talloc_free() in _mdssvc_open()

Jones Syue requested to merge samba-team/devel/samba:jones2019_mdssvc_early_free_in_mdssvc_open into master

Environment setup:

When macOS Finder connect to a samba server with 'spotlight = yes',

macOS would issue mdssvc open (mdssvc.opnum == 0) to samba and it goes

through api _mdssvc_open().

After applied 578e434a,

(this is reported by jaywei@qnap.com)

this line 'talloc_free(path);' is deleted if _mdssvc_open() normal exit,

so memory is lazy de-allocate: delayed to

smbd_tevent_trace_callback() @ smb2_process.c. [1]

Supposed to explicitly free 'path' in _mdssvc_open() @ srv_mdssvc_nt.c[2]

just like abnormal exit, do not wait for main loop to free 'path' which is

no longer used, this is more consistent while reading source code.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15449

[1] gdb tracing 'path' address 0x56204ccc67e0 to know how it is freed.
Breakpoint 2, _tc_free_children_internal (tc=0x56204ccc6780, ptr=0x56204ccc67e0, location=0x7ff430d96410 "../../lib/talloc/talloc.c:1714") at ../../lib/talloc/talloc.c:1656
1656            while (tc->child) {
(gdb) bt
0  _tc_free_children_internal (tc=0x56204ccc6780, ptr=0x56204ccc67e0, location=0x7ff430d96410 "../../lib/talloc/talloc.c:1714") at ../../lib/talloc/talloc.c:1656
1  0x00007ff430d92b14 in _tc_free_internal (tc=0x56204ccc6780, location=0x7ff430d96410 "../../lib/talloc/talloc.c:1714") at ../../lib/talloc/talloc.c:1183
2  0x00007ff430d93b71 in _tc_free_children_internal (tc=0x56204ccc6720, ptr=0x56204ccc6780, location=0x7ff430d96410 "../../lib/talloc/talloc.c:1714") at ../../lib/talloc/talloc.c:1668
3  0x00007ff430d93d66 in talloc_free_children (ptr=0x56204ccc6780) at ../../lib/talloc/talloc.c:1714
4  0x00007ff432235aca in talloc_pop (frame=0x56204ccc6780) at ../../lib/util/talloc_stack.c:125
5  0x00007ff430d92959 in _tc_free_internal (tc=0x56204ccc6720, location=0x7ff431f358d0 "../../source3/smbd/process.c:3726") at ../../lib/talloc/talloc.c:1157
6  0x00007ff430d92cd5 in _talloc_free_internal (ptr=0x56204ccc6780, location=0x7ff431f358d0 "../../source3/smbd/process.c:3726") at ../../lib/talloc/talloc.c:1247
7  0x00007ff430d93f96 in _talloc_free (ptr=0x56204ccc6780, location=0x7ff431f358d0 "../../source3/smbd/process.c:3726") at ../../lib/talloc/talloc.c:1791
8  0x00007ff431d81292 in smbd_tevent_trace_callback (point=TEVENT_TRACE_AFTER_LOOP_ONCE, private_data=0x7ffe46591e30) at ../../source3/smbd/process.c:3726
<...cut...>
[2] gdb tracing 'path' address 0x55a6d66deed0 to know how it is freed.
Breakpoint 2, _tc_free_children_internal (tc=0x55a6d66deed0, ptr=0x55a6d66def30, location=0x7fc4cca84040 "../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189") at ../../lib/talloc/talloc.c:1656
1656            while (tc->child) {
(gdb) bt
0  _tc_free_children_internal (tc=0x55a6d66deed0, ptr=0x55a6d66def30, location=0x7fc4cca84040 "../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189") at ../../lib/talloc/talloc.c:1656
1  0x00007fc4cb892b14 in _tc_free_internal (tc=0x55a6d66deed0, location=0x7fc4cca84040 "../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189") at ../../lib/talloc/talloc.c:1183
2  0x00007fc4cb892cd5 in _talloc_free_internal (ptr=0x55a6d66def30, location=0x7fc4cca84040 "../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189") at ../../lib/talloc/talloc.c:1247
3  0x00007fc4cb893f96 in _talloc_free (ptr=0x55a6d66def30, location=0x7fc4cca84040 "../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189") at ../../lib/talloc/talloc.c:1791
4  0x00007fc4cc9396e4 in _mdssvc_open (p=0x55a6d66d5600, r=0x55a6d66edc60) at ../../source3/rpc_server/mdssvc/srv_mdssvc_nt.c:189
<...cut...>

Checklist

  • Commits have Signed-off-by: with name/author being identical to the commit author
  • (optional) This MR is just one part towards a larger feature.
  • (optional, if backport required) Bugzilla bug filed and BUG: tag added
  • Test suite updated with functionality tests
  • Test suite updated with negative tests
  • Documentation updated
  • CI timeout is 3h or higher (see Settings/CICD/General pipelines/ Timeout)

Reviewer's checklist:

  • There is a test suite reasonably covering new functionality or modifications
  • Function naming, parameters, return values, types, etc., are consistent and according to README.Coding.md
  • This feature/change has adequate documentation added
  • No obvious mistakes in the code

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