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, 83 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/crypto.rst b/Documentation/admin-guide/sysctl/crypto.rst
new file mode 100644
index 000000000..9a1bd5328
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/crypto.rst
@@ -0,0 +1,83 @@
+=================
+/proc/sys/crypto/
+=================
+
+These files show up in ``/proc/sys/crypto/``, depending on the
+kernel configuration:
+
+.. contents:: :local:
+
+.. _af_alg_restrict:
+
+af_alg_restrict
+===============
+
+Controls the level of restriction of AF_ALG.
+
+AF_ALG is a deprecated and rarely-used userspace interface that is a
+frequent source of vulnerabilities. It also unnecessarily exposes a
+large number of kernel implementation details. For more information
+about AF_ALG, see :ref:`Documentation/crypto/userspace-if.rst
+<crypto_userspace_interface>`.
+
+Starting in Linux v7.3, AF_ALG supports only a limited set of
+algorithms by default. This sysctl allows the system administrator to
+remove this restriction when needed for compatibility reasons, or to
+go further and disable AF_ALG entirely. The default value is 1.
+
+===  ==================================================================
+0    AF_ALG is unrestricted.
+
+1    AF_ALG is supported with a limited list of algorithms. The list
+     is designed for compatibility with known users such as iwd and
+     bluez that haven't yet been fixed to use userspace crypto code.
+
+     Specifically, there is an allowlist for unprivileged processes
+     and a somewhat longer allowlist for processes that hold
+     CAP_SYS_ADMIN or CAP_NET_ADMIN in the initial user namespace.
+
+     Attempts to bind() an AF_ALG socket with a disallowed algorithm
+     fail with ENOENT.
+
+2    AF_ALG is completely disabled. Attempts to create an AF_ALG
+     socket fail with EAFNOSUPPORT.
+===  ==================================================================
+
+fips_enabled
+============
+
+Read-only flag that indicates whether FIPS mode is enabled.
+
+- ``0``: FIPS mode is disabled (default).
+- ``1``: FIPS mode is enabled.
+
+This value is set at boot time via the ``fips=1`` kernel command line
+parameter. When enabled, the cryptographic API will restrict the use
+of certain algorithms and perform self-tests to ensure compliance with
+FIPS (Federal Information Processing Standards) requirements, such as
+FIPS 140-2 and the newer FIPS 140-3, depending on the kernel
+configuration and the module in use.
+
+fips_name
+=========
+
+Read-only file that contains the name of the FIPS module currently in use.
+The value is typically configured via the ``CONFIG_CRYPTO_FIPS_NAME``
+kernel configuration option.
+
+fips_version
+============
+
+Read-only file that contains the version string of the FIPS module.
+If ``CONFIG_CRYPTO_FIPS_CUSTOM_VERSION`` is set, it uses the value from
+``CONFIG_CRYPTO_FIPS_VERSION``. Otherwise, it defaults to the kernel
+release version (``UTS_RELEASE``).
+
+Copyright (c) 2026, Shubham Chakraborty <chakrabortyshubham66@gmail.com>
+
+For general info and legal blurb, please look in
+Documentation/admin-guide/sysctl/index.rst.
+
+.. See scripts/check-sysctl-docs to keep this up to date:
+.. scripts/check-sysctl-docs -vtable="crypto" \
+..         $(git grep -l register_sysctl_)