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In case we don't have either a /var/log/samba directory, or pass a
non-existent log directory through '-l' option, all commands that are
daemonized with '-D' option hang when executed within a subshell.
An example on how to trigger that:
# rm -r /var/log/samba
# s=$(nmbd -D -s /etc/samba/smb.conf -l /foo123)
(never returns)
So, when the above command is executed within a subshell the following
happens:
(a) Parent shell creates a pipe, sets write side of it to fd 1
(stdout), call read() on read-side fd, forks off a new child process
and then executes nmbd in it.
(b) nmbd sets up initial logging to go through fd 1 (stdout) by
calling setup_logging(..., DEBUG_DEFAULT_STDOUT). 'state.fd' is now
set to 1.
(c) reopen_logs() is called by the first time which then calls
reopen_logs_internal()
(d) in reopen_logs_internal(), it attempts to create log.nmbd file in
/foo123 directory and fails because directory doesn't exist.
(e) Regardless whether the log file was created or not, it calls
dup2(state.fd, 2) which dups fd 1 into fd 2.
(f) At some point, fd 0 and 1 are closed and set to /dev/null
The problem with that is because parent shell in (a) is still blocked in
read() call and the new write side of the pipe is now fd 2 -- after
dup2() in (e) -- and remains unclosed.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=13578
Signed-off-by: Paulo Alcantara <palcantara@suse.de>
Reviewed-by: Jim McDonough <jmcd@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Autobuild-User(master): Jeremy Allison <jra@samba.org>
Autobuild-Date(master): Sat Aug 18 01:32:25 CEST 2018 on sn-devel-144
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|---|---|---|
| .. | ||
| addns | ||
| afs | ||
| async_req | ||
| audit_logging | ||
| compression | ||
| crypto | ||
| dbwrap | ||
| krb5_wrap | ||
| ldb | ||
| ldb-samba | ||
| mscat | ||
| param | ||
| pthreadpool | ||
| replace | ||
| smbconf | ||
| socket | ||
| talloc | ||
| tdb | ||
| tdb_wrap | ||
| tdr | ||
| tevent | ||
| texpect | ||
| torture | ||
| tsocket | ||
| util | ||
| README | ||
| wscript_build | ||
compression - Various compression algorithms (MSZIP, lzxpress)
dnspython - Python module for working with DNS.
popt - Command-line option parsing library
replace - Provides replacements for standard (POSIX, C99) functions
not provided by the host platform.
subunit - Utilities and bindings for working with the Subunit test result
reporting protocol.
talloc - Hierarchical pool based memory allocator
tdb - Simple but fast key/value database library, supporting multiple writers
torture - Simple unit testing helper library