thr3ads.net - samba - [Samba] [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system. [Apr 2022]

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Jaideep Shankar

2022-Apr-07 08:30 UTC

[Samba] [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system.

Yes, SMB version on Windows 10 is given.

Contents of the smb config file:

#
# Sample configuration file for the Samba suite for Debian GNU/Linux.
#
#
# This is the main Samba configuration file. You should read the
# smb.conf(5) manual page in order to understand the options listed
# here. Samba has a huge number of configurable options most of which 
# are not shown in this example
#
# Some options that are often worth tuning have been included as
# commented-out examples in this file.
#  - When such options are commented with ";", the proposed setting
#    differs from the default Samba behaviour
#  - When commented with "#", the proposed setting is the default
#    behaviour of Samba but the option is considered important
#    enough to be mentioned here
#
# NOTE: Whenever you modify this file you should run the command
# "testparm" to check that you have not made any basic syntactic 
# errors. 

#======================= Global Settings ======================
[global]

## Browsing/Identification ###

# Change this to the workgroup/NT-domain name your Samba server will part of
   workgroup = WORKGROUP

# server string is the equivalent of the NT Description field
   server string = %h server (Samba, Ubuntu)

#### Networking ####

# The specific set of interfaces / networks to bind to
# This can be either the interface name or an IP address/netmask;
# interface names are normally preferred
;   interfaces = 127.0.0.0/8 eth0

# Only bind to the named interfaces and/or networks; you must use the
# 'interfaces' option above to use this.
# It is recommended that you enable this feature if your Samba machine is
# not protected by a firewall or is a firewall itself.  However, this
# option cannot handle dynamic or non-broadcast interfaces correctly.
;   bind interfaces only = yes

#### Debugging/Accounting ####

# This tells Samba to use a separate log file for each machine
# that connects
   log file = /var/log/samba/log.%m

# Cap the size of the individual log files (in KiB).
   max log size = 1000

# We want Samba to only log to /var/log/samba/log.{smbd,nmbd}.
# Append syslog at 1 if you want important messages to be sent to syslog too.
   logging = file

# Do something sensible when Samba crashes: mail the admin a backtrace
   panic action = /usr/share/samba/panic-action %d

####### Authentication #######

# Server role. Defines in which mode Samba will operate. Possible
# values are "standalone server", "member server",
"classic primary
# domain controller", "classic backup domain controller",
"active
# directory domain controller". 
#
# Most people will want "standalone server" or "member
server".
# Running as "active directory domain controller" will require first
# running "samba-tool domain provision" to wipe databases and create a
# new domain.
   server role = standalone server

   obey pam restrictions = yes

# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
   unix password sync = yes

# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan <<kahan at
informatik.tu-muenchen.de> for
# sending the correct chat script for the passwd program in Debian Sarge).
   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:*
%n\n *password\supdated\ssuccessfully* .

# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# 'passwd program'. The default is 'no'.
   pam password change = yes

# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
   map to guest = bad user

########## Domains ###########

#
# The following settings only takes effect if 'server role = primary
# classic domain controller', 'server role = backup domain
controller'
# or 'domain logons' is set 
#

# It specifies the location of the user's
# profile directory from the client point of view) The following
# required a [profiles] share to be setup on the samba server (see
# below)
;   logon path = \\%N\profiles\%U
# Another common choice is storing the profile in the user's home directory
# (this is Samba's default)
#   logon path = \\%N\%U\profile

# The following setting only takes effect if 'domain logons' is set
# It specifies the location of a user's home directory (from the client
# point of view)
;   logon drive = H:
#   logon home = \\%N\%U

# The following setting only takes effect if 'domain logons' is set
# It specifies the script to run during logon. The script must be stored
# in the [netlogon] share
# NOTE: Must be store in 'DOS' file format convention
;   logon script = logon.cmd

# This allows Unix users to be created on the domain controller via the SAMR
# RPC pipe.  The example command creates a user account with a disabled Unix
# password; please adapt to your needs
; add user script = /usr/sbin/adduser --quiet --disabled-password --gecos
"" %u

# This allows machine accounts to be created on the domain controller via the 
# SAMR RPC pipe.  
# The following assumes a "machines" group exists on the system
; add machine script  = /usr/sbin/useradd -g machines -c "%u machine
account" -d /var/lib/samba -s /bin/false %u

# This allows Unix groups to be created on the domain controller via the SAMR
# RPC pipe.  
; add group script = /usr/sbin/addgroup --force-badname %g

############ Misc ############

# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting
;   include = /home/samba/etc/smb.conf.%m

# Some defaults for winbind (make sure you're not using the ranges
# for something else.)
;   idmap config * :              backend = tdb
;   idmap config * :              range   = 3000-7999
;   idmap config YOURDOMAINHERE : backend = tdb
;   idmap config YOURDOMAINHERE : range   = 100000-999999
;   template shell = /bin/bash

# Setup usershare options to enable non-root users to share folders
# with the net usershare command.

# Maximum number of usershare. 0 means that usershare is disabled.
#   usershare max shares = 100

# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
   usershare allow guests = yes

#======================= Share Definitions ======================
# Un-comment the following (and tweak the other settings below to suit)
# to enable the default home directory shares. This will share each
# user's home directory as \\server\username
;[homes]
;   comment = Home Directories
;   browseable = no

# By default, the home directories are exported read-only. Change the
# next parameter to 'no' if you want to be able to write to them.
;   read only = yes

# File creation mask is set to 0700 for security reasons. If you want to
# create files with group=rw permissions, set next parameter to 0775.
;   create mask = 0700

# Directory creation mask is set to 0700 for security reasons. If you want to
# create dirs. with group=rw permissions, set next parameter to 0775.
;   directory mask = 0700

# By default, \\server\username shares can be connected to by anyone
# with access to the samba server.
# Un-comment the following parameter to make sure that only "username"
# can connect to \\server\username
# This might need tweaking when using external authentication schemes
;   valid users = %S

# Un-comment the following and create the netlogon directory for Domain Logons
# (you need to configure Samba to act as a domain controller too.)
;[netlogon]
;   comment = Network Logon Service
;   path = /home/samba/netlogon
;   guest ok = yes
;   read only = yes

# Un-comment the following and create the profiles directory to store
# users profiles (see the "logon path" option above)
# (you need to configure Samba to act as a domain controller too.)
# The path below should be writable by all users so that their
# profile directory may be created the first time they log on
;[profiles]
;   comment = Users profiles
;   path = /home/samba/profiles
;   guest ok = no
;   browseable = no
;   create mask = 0600
;   directory mask = 0700

[printers]
   comment = All Printers
   browseable = no
   path = /var/spool/samba
   printable = yes
   guest ok = no
   read only = yes
   create mask = 0700

# Windows clients look for this share name as a source of downloadable
# printer drivers
[print$]
   comment = Printer Drivers
   path = /var/lib/samba/printers
   browseable = yes
   read only = yes
   guest ok = no
# Uncomment to allow remote administration of Windows print drivers.
# You may need to replace 'lpadmin' with the name of the group your
# admin users are members of.
# Please note that you also need to set appropriate Unix permissions
# to the drivers directory for these users to have write rights in it
;   write list = root, @lpadmin

[sambasharero]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = yes
    browsable = yes

[sambasharero1]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = yes
    browsable = yes

[sambasharero2]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = no
    browsable = yes

[sambasharero3]
	comment = Samba on Ubuntu ro
	path = /home/ubuntu/smbro
	read only = yes
	browsable = yes

[sambasharerw]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = no
    browsable = yes

[sambashare]
    comment = Samba on Ubuntu
    path = /home/ubuntu/smb
    read only = no
    browsable = yes

Regards,
Jaideep

-----Original Message-----
From: samba <samba-bounces at lists.samba.org> On Behalf Of Rowland Penny
via samba
Sent: 07 April 2022 13:56
To: samba at lists.samba.org
Cc: Rowland Penny <rpenny at samba.org>
Subject: [EXTERNAL]:Re: [Samba] A disconnected network can, for all practical
purposes, hang your system.

Caution: This email originated from outside the organization. Do not click links
or open attachments, unless you recognize the sender and know the content is
safe.

On Thu, 2022-04-07 at 08:17 +0000, Jaideep Shankar via samba
wrote:> Hi,
>
> Record locks taken on a remote file remains valid, even after 1 hour 
> of network disconnection. The following test case describes the set of 
> activities done in chronological order:
>
>
>   *   A process (P1) on a windows client (C1) and another process
> (P2) on a Linux client (C2) are connected to a common Linux server and 
> accessing the same remote file.
>   *   Both P1 and P2 opens the remote file and gets a handle each.
>   *   P1 takes exclusive lock on offset 0.
>   *   P2 tries to take exclusive lock on offset 0 in a loop but does
> not get since P1 holds an exclusive lock on the same offset.
>   *   Now, P1 is disconnected from remote file (C1 is disconnected
> from server).
>
> Result: P2 does not get lock, returns 'EACCES' instantaneously,
tried
> for around an hour.
>
> The results were surprising, since in a Wi-Fi environment, where 
> systems keep coming in and out, it can potentially stall the system.
>
> OS specs of C1                                   - Windows 10
> Enterprise (version: 20H2, build: 19042.1237)
> OS specs of C2                                   - Ubuntu 20.04.3 LTS
> (GNU/Linux 5.13.0-1021-azure x86_64)
> OS specs of Linux Server                - Ubuntu 20.04.1 LTS
> (GNU/Linux 5.13.0-37-generic x86_64)
>
> Samba version on C2                      - 4.13.17-
> Ubuntu                                            Command used -
> smbststus
> Samba version on Linux server   - 4.13.17-
> Ubuntu                                              Command used -
> smbstatus
> Samba version on C1                      -
> SMBv2/v3                                                      Command
I think you mean SMB version used the Win10, Samba is a Unix program that
emulates SMB.
> >
> Protocol version                               - 3.1.1 (same on both
> connections)           Command used - smbstatus
>
> The smb config file on the Linux server is also attached.
This list strips attachments, so can you post the smb.conf inline.

Rowland

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Rowland Penny

2022-Apr-07 09:06 UTC

head link

[Samba] [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system.

On Thu, 2022-04-07 at 08:30 +0000, Jaideep Shankar
wrote:> Yes, SMB version on Windows 10 is given.
OK, but you called it 'Samba' :-)
> 
> Contents of the smb config file:
Without all the comments and defaults (aka the output of 'testparm -s):

[global]
   workgroup = WORKGROUP
   server string = %h server (Samba, Ubuntu)
   log file = /var/log/samba/log.%m
   max log size = 1000
   logging = file
   panic action = /usr/share/samba/panic-action %d
   server role = standalone server
   obey pam restrictions = yes
   unix password sync = yes
   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\s*\spassword:* %n\n
*Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
   pam password change = yes
   map to guest = bad user
   usershare allow guests = yes

[printers]
   comment = All Printers
   browseable = no
   path = /var/spool/samba
   printable = yes
   create mask = 0700

[print$]
   comment = Printer Drivers
   path = /var/lib/samba/printers

[sambasharero]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro

[sambasharero1]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro

[sambasharero2]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = no

[sambasharero3]
        comment = Samba on Ubuntu ro
        path = /home/ubuntu/smbro

[sambasharerw]
    comment = Samba on Ubuntu ro
    path = /home/ubuntu/smbro
    read only = no

[sambashare]
    comment = Samba on Ubuntu
    path = /home/ubuntu/smb
    read only = no

Have you tried connecting from two Linux machines ? If so, do you get
the same result ? It is possible that the Win10 machine is not
releasing the lock.

Rowland

samba - Apr 2022 - [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system.

[Samba] [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system.

[Samba] [EXTERNAL]:Re: A disconnected network can, for all practical purposes, hang your system.