[Samba] samba 4.9.5 smbd panic

[Ralph Boehme]

Am 1/24/20 um 12:23 PM schrieb Andrea Cucciarre' via samba:
> Hello,
> 
> I have the logs with log level set to 10.
> May I know which log file do you need? The panic message seems to be the
> same as when happened with log level set to 2 (attached below) and many
> clients were accessing the share so there are a lot of logs.
> I can't reproduce it in my lab tests, so It would help me to run more
> specific tests if you could explain me what smbd was doing when the
> panic occurred.

it was doing a server-side copy when the connection was disconnected by
the client, so smbd ran its teardown stuff.

As part of teardown a bunch of state destructors are executed, ending up
in a cleanup function for the server-side copy state:
vfswrap_offload_write_cleanup()

That function called stuff which wanted to perform impersonation and
there we crashed in the impersonation code.

As there have been a myriad of changes to the impersonation code since
the version you're using, please try to reproduce the issue with a
current Samba from git master. If the problem persists, please ensure
you configure with --enable-developer which should enabled debug symbols
and should set panic action to sleep.

When you reproduce the crash, the crashing process will sleep() so you
can attach with gdb and get a full backtrace with symbols:

# gdb -p PID
# bt full
...

-slow

-- 
Ralph Boehme, Samba Team                https://samba.org/
Samba Developer, SerNet GmbH   https://sernet.de/en/samba/
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