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-skcipher.rst b/Documentation/crypto/api-skcipher.rst
new file mode 100644
index 000000000..4b7c81607
--- /dev/null
+++ b/Documentation/crypto/api-skcipher.rst
@@ -0,0 +1,38 @@
+Symmetric Key Cipher
+====================
+
+Block Cipher Algorithm Definitions
+----------------------------------
+
+.. kernel-doc:: include/linux/crypto.h
+   :doc: Block Cipher Algorithm Definitions
+
+.. kernel-doc:: include/linux/crypto.h
+   :functions: crypto_alg cipher_alg compress_alg
+
+Symmetric Key Cipher API
+------------------------
+
+.. kernel-doc:: include/crypto/skcipher.h
+   :doc: Symmetric Key Cipher API
+
+.. kernel-doc:: include/crypto/skcipher.h
+   :functions: crypto_alloc_skcipher crypto_free_skcipher crypto_has_skcipher crypto_skcipher_ivsize crypto_skcipher_blocksize crypto_skcipher_setkey crypto_skcipher_reqtfm crypto_skcipher_encrypt crypto_skcipher_decrypt
+
+Symmetric Key Cipher Request Handle
+-----------------------------------
+
+.. kernel-doc:: include/crypto/skcipher.h
+   :doc: Symmetric Key Cipher Request Handle
+
+.. kernel-doc:: include/crypto/skcipher.h
+   :functions: crypto_skcipher_reqsize skcipher_request_set_tfm skcipher_request_alloc skcipher_request_free skcipher_request_set_callback skcipher_request_set_crypt
+
+Single Block Cipher API
+-----------------------
+
+.. kernel-doc:: include/crypto/internal/cipher.h
+   :doc: Single Block Cipher API
+
+.. kernel-doc:: include/crypto/internal/cipher.h
+   :functions: crypto_alloc_cipher crypto_free_cipher crypto_has_cipher crypto_cipher_blocksize crypto_cipher_setkey crypto_cipher_encrypt_one crypto_cipher_decrypt_one