thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 107 insertions, 0 deletions

diff --git a/Documentation/usb/linux-cdc-acm.inf b/Documentation/usb/linux-cdc-acm.inf
new file mode 100644
index 000000000..f0ffc27d4
--- /dev/null
+++ b/Documentation/usb/linux-cdc-acm.inf
@@ -0,0 +1,107 @@
+; Windows USB CDC ACM Setup File
+
+; Based on INF template which was:
+;     Copyright (c) 2000 Microsoft Corporation
+;     Copyright (c) 2007 Microchip Technology Inc.
+; likely to be covered by the MLPL as found at:
+;    <http://msdn.microsoft.com/en-us/cc300389.aspx#MLPL>.
+; For use only on Windows operating systems.
+
+[Version]
+Signature="$Windows NT$"
+Class=Ports
+ClassGuid={4D36E978-E325-11CE-BFC1-08002BE10318}
+Provider=%Linux%
+DriverVer=11/15/2007,5.1.2600.0
+
+[Manufacturer]
+%Linux%=DeviceList, NTamd64
+
+[DestinationDirs]
+DefaultDestDir=12
+
+
+;------------------------------------------------------------------------------
+;  Windows 2000/XP/Vista-32bit Sections
+;------------------------------------------------------------------------------
+
+[DriverInstall.nt]
+include=mdmcpq.inf
+CopyFiles=DriverCopyFiles.nt
+AddReg=DriverInstall.nt.AddReg
+
+[DriverCopyFiles.nt]
+usbser.sys,,,0x20
+
+[DriverInstall.nt.AddReg]
+HKR,,DevLoader,,*ntkern
+HKR,,NTMPDriver,,USBSER.sys
+HKR,,EnumPropPages32,,"MsPorts.dll,SerialPortPropPageProvider"
+
+[DriverInstall.nt.Services]
+AddService=usbser, 0x00000002, DriverService.nt
+
+[DriverService.nt]
+DisplayName=%SERVICE%
+ServiceType=1
+StartType=3
+ErrorControl=1
+ServiceBinary=%12%\USBSER.sys
+
+;------------------------------------------------------------------------------
+;  Vista-64bit Sections
+;------------------------------------------------------------------------------
+
+[DriverInstall.NTamd64]
+include=mdmcpq.inf
+CopyFiles=DriverCopyFiles.NTamd64
+AddReg=DriverInstall.NTamd64.AddReg
+
+[DriverCopyFiles.NTamd64]
+USBSER.sys,,,0x20
+
+[DriverInstall.NTamd64.AddReg]
+HKR,,DevLoader,,*ntkern
+HKR,,NTMPDriver,,USBSER.sys
+HKR,,EnumPropPages32,,"MsPorts.dll,SerialPortPropPageProvider"
+
+[DriverInstall.NTamd64.Services]
+AddService=usbser, 0x00000002, DriverService.NTamd64
+
+[DriverService.NTamd64]
+DisplayName=%SERVICE%
+ServiceType=1
+StartType=3
+ErrorControl=1
+ServiceBinary=%12%\USBSER.sys
+
+
+;------------------------------------------------------------------------------
+;  Vendor and Product ID Definitions
+;------------------------------------------------------------------------------
+; When developing your USB device, the VID and PID used in the PC side
+; application program and the firmware on the microcontroller must match.
+; Modify the below line to use your VID and PID.  Use the format as shown
+; below.
+; Note: One INF file can be used for multiple devices with different
+;       VID and PIDs.  For each supported device, append
+;       ",USB\VID_xxxx&PID_yyyy" to the end of the line.
+;------------------------------------------------------------------------------
+[SourceDisksFiles]
+[SourceDisksNames]
+[DeviceList]
+%DESCRIPTION%=DriverInstall, USB\VID_0525&PID_A4A7, USB\VID_1D6B&PID_0104&MI_02, USB\VID_1D6B&PID_0106&MI_00
+
+[DeviceList.NTamd64]
+%DESCRIPTION%=DriverInstall, USB\VID_0525&PID_A4A7, USB\VID_1D6B&PID_0104&MI_02, USB\VID_1D6B&PID_0106&MI_00
+
+
+;------------------------------------------------------------------------------
+;  String Definitions
+;------------------------------------------------------------------------------
+;Modify these strings to customize your device
+;------------------------------------------------------------------------------
+[Strings]
+Linux               = "Linux Developer Community"
+DESCRIPTION         = "Gadget Serial"
+SERVICE             = "USB RS-232 Emulation Driver"