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, 129 insertions, 0 deletions

diff --git a/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst b/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst
new file mode 100644
index 000000000..8258a72f0
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/dm-inlinecrypt.rst
@@ -0,0 +1,129 @@
+==============
+dm-inlinecrypt
+==============
+
+Device-Mapper's "inlinecrypt" target provides transparent encryption of block devices
+using the inline encryption hardware.
+
+For a more detailed description of inline encryption, see:
+https://docs.kernel.org/block/inline-encryption.html
+
+Parameters::
+
+	      <cipher> <key> <iv_offset> <device path> \
+	      <offset> [<#opt_params> <opt_params>]
+
+<cipher>
+    Encryption cipher type.
+
+    The cipher specifications format is::
+
+       cipher
+
+    Examples::
+
+       aes-xts-plain64
+
+    The cipher type corresponds to the encryption modes supported by
+    inline crypto in the block layer. Currently, only
+    BLK_ENCRYPTION_MODE_AES_256_XTS (i.e. aes-xts-plain64) is supported.
+
+<key>
+    Key used for encryption. It is encoded either as a hexadecimal number
+    or it can be passed as <key_string> prefixed with single colon
+    character (':') for keys residing in kernel keyring service.
+    You can only use key sizes that are valid for the selected cipher.
+    Note that the size in bytes of a valid key must be in below range.
+
+        [BLK_CRYPTO_KEY_TYPE_RAW, BLK_CRYPTO_KEY_TYPE_HW_WRAPPED]
+
+<key_string>
+    The kernel keyring key is identified by string in following format:
+    <key_size>:<keyring_type>:<key_description>.
+
+<key_size>
+    The encryption key size in bytes. The kernel key payload size must match
+    the value passed in <key_size>.
+
+<keyring_type>
+    The type of the key inside the kernel keyring. It can be either 'logon',
+    or 'trusted' kernel key type.
+
+<key_description>
+    The kernel keyring key description inlinecrypt target should look for
+    when loading key of <keyring_type>.
+
+<iv_offset>
+    The IV offset is a sector count that is added to the sector number
+    before creating the IV.
+
+<device path>
+    This is the device that is going to be used as backend and contains the
+    encrypted data.  You can specify it as a path like /dev/xxx or a device
+    number <major>:<minor>.
+
+<offset>
+    Starting sector within the device where the encrypted data begins.
+
+<#opt_params>
+    Number of optional parameters. If there are no optional parameters,
+    the optional parameters section can be skipped or #opt_params can be zero.
+    Otherwise #opt_params is the number of following arguments.
+
+    Example of optional parameters section:
+        keytype:raw allow_discards sector_size:4096 iv_large_sectors
+
+<key_type>
+    The type of the key as seen by the block layer, either standard or
+    hardware-wrapped. The string is supplied in the table as <keytype:raw>
+    or <keytype:hw-wrapped>.
+
+allow_discards
+    Block discard requests (a.k.a. TRIM) are passed through the inlinecrypt
+    device. The default is to ignore discard requests.
+
+    WARNING: Assess the specific security risks carefully before enabling this
+    option.  For example, allowing discards on encrypted devices may lead to
+    the leak of information about the ciphertext device (filesystem type,
+    used space etc.) if the discarded blocks can be located easily on the
+    device later.
+
+sector_size:<bytes>
+    Use <bytes> as the encryption unit instead of 512 bytes sectors.
+    This option can be in range 512 - 4096 bytes and must be power of two.
+    Virtual device will announce this size as a minimal IO and logical sector.
+
+iv_large_sectors
+    Use <sector_size>-based sector numbers for IV generation instead of
+    512-byte sectors.
+
+    For dm-inlinecrypt, this flag must be specified when <sector_size>
+    is larger than 512 bytes. The legacy 512-byte-based IV behavior is
+    not supported.
+
+    When specified, if <sector_size> is 4096 bytes, plain64 IV for the
+    second sector will be 1, and <iv_offset> must be a multiple of
+    <sector_size> (in 512-byte units).
+
+Example scripts
+===============
+Currently, dm-inlinecrypt devices must be set up directly using dmsetup.
+There is no userspace support yet to integrate dm-inlinecrypt with LUKS
+or cryptsetup. In particular, cryptsetup currently only supports
+dm-crypt, and cannot be used to create dm-inlinecrypt mappings.
+
+The following examples demonstrate how to create dm-inlinecrypt devices
+using dmsetup
+
+::
+
+	#!/bin/sh
+	# Create a inlinecrypt device using dmsetup
+	dmsetup create inlinecrypt1 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 0 $1 0 1 keytype:raw"
+
+::
+
+	#!/bin/sh
+	# Create a inlinecrypt device using dmsetup when encryption key is stored in keyring service
+	dmsetup create inlinecrypt2 --table "0 `blockdev --getsz $1` inlinecrypt aes-xts-plain64 :64:logon:fde:dminlinecrypt_test_key 0 0 $1 0 1 keytype:raw"
+