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, 66 insertions, 0 deletions

diff --git a/Documentation/usb/linux.inf b/Documentation/usb/linux.inf
new file mode 100644
index 000000000..c569ac6be
--- /dev/null
+++ b/Documentation/usb/linux.inf
@@ -0,0 +1,66 @@
+; Based on template INF file found at
+;    <https://msdn.microsoft.com/en-us/library/ff570620.aspx>
+; which was:
+;    Copyright (c) Microsoft Corporation
+; and released under 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               = Net
+ClassGUID           = {4d36e972-e325-11ce-bfc1-08002be10318}
+Provider            = %Linux%
+DriverVer           = 06/21/2006,6.0.6000.16384
+
+[Manufacturer]
+%Linux%             = LinuxDevices,NTx86,NTamd64,NTia64
+
+; Decoration for x86 architecture
+[LinuxDevices.NTx86]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+; Decoration for x64 architecture
+[LinuxDevices.NTamd64]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+; Decoration for ia64 architecture
+[LinuxDevices.NTia64]
+%LinuxDevice%       = RNDIS.NT.5.1, USB\VID_0525&PID_a4a2, USB\VID_1d6b&PID_0104&MI_00
+
+;@@@ This is the common setting for setup
+[ControlFlags]
+ExcludeFromSelect=*
+
+; DDInstall section
+; References the in-build Netrndis.inf
+[RNDIS.NT.5.1]
+Characteristics     = 0x84   ; NCF_PHYSICAL + NCF_HAS_UI
+BusType             = 15
+; NEVER REMOVE THE FOLLOWING REFERENCE FOR NETRNDIS.INF
+include             = netrndis.inf
+needs               = Usb_Rndis.ndi
+AddReg              = Rndis_AddReg_Vista
+
+; DDInstal.Services section
+[RNDIS.NT.5.1.Services]
+include             = netrndis.inf
+needs               = Usb_Rndis.ndi.Services
+
+; Optional registry settings. You can modify as needed.
+[RNDIS_AddReg_Vista]
+HKR, NDI\params\VistaProperty, ParamDesc,  0, %Vista_Property%
+HKR, NDI\params\VistaProperty, type,       0, "edit"
+HKR, NDI\params\VistaProperty, LimitText,  0, "12"
+HKR, NDI\params\VistaProperty, UpperCase,  0, "1"
+HKR, NDI\params\VistaProperty, default,    0, " "
+HKR, NDI\params\VistaProperty, optional,   0, "1"
+
+; No sys copyfiles - the sys files are already in-build
+; (part of the operating system).
+; We do not support XP SP1-, 2003 SP1-, ME, 9x.
+
+[Strings]
+Linux                 = "Linux Developer Community"
+LinuxDevice           = "Linux USB Ethernet/RNDIS Gadget"
+Vista_Property        = "Optional Vista Property"