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, 58 insertions, 0 deletions

diff --git a/include/crypto/internal/engine.h b/include/crypto/internal/engine.h
new file mode 100644
index 000000000..6a1d27880
--- /dev/null
+++ b/include/crypto/internal/engine.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Crypto engine API
+ *
+ * Copyright (c) 2016 Baolin Wang <baolin.wang@linaro.org>
+ * Copyright (c) 2023 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+#ifndef _CRYPTO_INTERNAL_ENGINE_H
+#define _CRYPTO_INTERNAL_ENGINE_H
+
+#include <crypto/algapi.h>
+#include <crypto/engine.h>
+#include <linux/kthread.h>
+#include <linux/spinlock_types.h>
+#include <linux/types.h>
+
+#define ENGINE_NAME_LEN	30
+
+struct device;
+
+/*
+ * struct crypto_engine - crypto hardware engine
+ * @name: the engine name
+ * @busy: request pump is busy
+ * @running: the engine is on working
+ * @retry_support: indication that the hardware allows re-execution
+ * of a failed backlog request
+ * crypto-engine, in head position to keep order
+ * @rt: whether this queue is set to run as a realtime task
+ * @list: link with the global crypto engine list
+ * @queue_lock: spinlock to synchronise access to request queue
+ * @queue: the crypto queue of the engine
+ * @kworker: kthread worker struct for request pump
+ * @pump_requests: work struct for scheduling work to the request pump
+ * @priv_data: the engine private data
+ * @cur_req: the current request which is on processing
+ */
+struct crypto_engine {
+	char			name[ENGINE_NAME_LEN];
+	bool			busy;
+	bool			running;
+
+	bool			retry_support;
+	bool			rt;
+
+	struct list_head	list;
+	spinlock_t		queue_lock;
+	struct crypto_queue	queue __guarded_by(&queue_lock);
+	struct device		*dev;
+
+	struct kthread_worker           *kworker;
+	struct kthread_work             pump_requests;
+
+	void				*priv_data;
+	struct crypto_async_request	*cur_req;
+};
+
+#endif