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, 62 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/nios2/nios2.txt b/Documentation/devicetree/bindings/nios2/nios2.txt
new file mode 100644
index 000000000..3e9cabe66
--- /dev/null
+++ b/Documentation/devicetree/bindings/nios2/nios2.txt
@@ -0,0 +1,62 @@
+* Nios II Processor Binding
+
+This binding specifies what properties available in the device tree
+representation of a Nios II Processor Core.
+
+Users can use sopc2dts tool for generating device tree sources (dts) from a
+Qsys system. See more detail in: http://www.alterawiki.com/wiki/Sopc2dts
+
+Required properties:
+
+- compatible: Compatible property value should be "altr,nios2-1.0".
+- reg: Contains CPU index.
+- interrupt-controller: Specifies that the node is an interrupt controller
+- #interrupt-cells: Specifies the number of cells needed to encode an
+		interrupt source, should be 1.
+- clock-frequency: Contains the clock frequency for CPU, in Hz.
+- dcache-line-size: Contains data cache line size.
+- icache-line-size: Contains instruction line size.
+- dcache-size: Contains data cache size.
+- icache-size: Contains instruction cache size.
+- altr,pid-num-bits: Specifies the number of bits to use to represent the process
+		identifier (PID).
+- altr,tlb-num-ways: Specifies the number of set-associativity ways in the TLB.
+- altr,tlb-num-entries: Specifies the number of entries in the TLB.
+- altr,tlb-ptr-sz: Specifies size of TLB pointer.
+- altr,has-mul: Specifies CPU hardware multiply support, should be 1.
+- altr,has-mmu: Specifies CPU support MMU support, should be 1.
+- altr,has-initda: Specifies CPU support initda instruction, should be 1.
+- altr,reset-addr: Specifies CPU reset address
+- altr,fast-tlb-miss-addr: Specifies CPU fast TLB miss exception address
+- altr,exception-addr: Specifies CPU exception address
+
+Optional properties:
+- altr,has-div: Specifies CPU hardware divide support
+- altr,implementation: Nios II core implementation, this should be "fast";
+
+Example:
+
+cpu@0 {
+	device_type = "cpu";
+	compatible = "altr,nios2-1.0";
+	reg = <0>;
+	interrupt-controller;
+	#interrupt-cells = <1>;
+	clock-frequency = <125000000>;
+	dcache-line-size = <32>;
+	icache-line-size = <32>;
+	dcache-size = <32768>;
+	icache-size = <32768>;
+	altr,implementation = "fast";
+	altr,pid-num-bits = <8>;
+	altr,tlb-num-ways = <16>;
+	altr,tlb-num-entries = <128>;
+	altr,tlb-ptr-sz = <7>;
+	altr,has-div = <1>;
+	altr,has-mul = <1>;
+	altr,reset-addr = <0xc2800000>;
+	altr,fast-tlb-miss-addr = <0xc7fff400>;
+	altr,exception-addr = <0xd0000020>;
+	altr,has-initda = <1>;
+	altr,has-mmu = <1>;
+};