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, 38 insertions, 0 deletions

diff --git a/Documentation/crypto/api-digest.rst b/Documentation/crypto/api-digest.rst
new file mode 100644
index 000000000..02a2bcc26
--- /dev/null
+++ b/Documentation/crypto/api-digest.rst
@@ -0,0 +1,38 @@
+Message Digest
+==============
+
+Message Digest Algorithm Definitions
+------------------------------------
+
+.. kernel-doc:: include/crypto/hash.h
+   :doc: Message Digest Algorithm Definitions
+
+.. kernel-doc:: include/crypto/hash.h
+   :functions: hash_alg_common ahash_alg shash_alg
+
+Asynchronous Message Digest API
+-------------------------------
+
+.. kernel-doc:: include/crypto/hash.h
+   :doc: Asynchronous Message Digest API
+
+.. kernel-doc:: include/crypto/hash.h
+   :functions: crypto_alloc_ahash crypto_free_ahash crypto_ahash_init crypto_ahash_digestsize crypto_ahash_reqtfm crypto_ahash_reqsize crypto_ahash_statesize crypto_ahash_setkey crypto_ahash_finup crypto_ahash_final crypto_ahash_digest crypto_ahash_export crypto_ahash_import
+
+Asynchronous Hash Request Handle
+--------------------------------
+
+.. kernel-doc:: include/crypto/hash.h
+   :doc: Asynchronous Hash Request Handle
+
+.. kernel-doc:: include/crypto/hash.h
+   :functions: ahash_request_set_tfm ahash_request_alloc ahash_request_free ahash_request_set_callback ahash_request_set_crypt
+
+Synchronous Message Digest API
+------------------------------
+
+.. kernel-doc:: include/crypto/hash.h
+   :doc: Synchronous Message Digest API
+
+.. kernel-doc:: include/crypto/hash.h
+   :functions: crypto_alloc_shash crypto_free_shash crypto_shash_blocksize crypto_shash_digestsize crypto_shash_descsize crypto_shash_setkey crypto_shash_digest crypto_shash_export crypto_shash_import crypto_shash_init crypto_shash_update crypto_shash_final crypto_shash_finup