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/include/memory/renesas-rpc-if.h b/include/memory/renesas-rpc-if.h
new file mode 100644
index 000000000..53663c4e5
--- /dev/null
+++ b/include/memory/renesas-rpc-if.h
@@ -0,0 +1,83 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Renesas RPC-IF core driver
+ *
+ * Copyright (C) 2018~2019 Renesas Solutions Corp.
+ * Copyright (C) 2019 Macronix International Co., Ltd.
+ * Copyright (C) 2019-2020 Cogent Embedded, Inc.
+ */
+
+#ifndef __RENESAS_RPC_IF_H
+#define __RENESAS_RPC_IF_H
+
+#include <linux/pm_runtime.h>
+#include <linux/types.h>
+
+enum rpcif_data_dir {
+	RPCIF_NO_DATA,
+	RPCIF_DATA_IN,
+	RPCIF_DATA_OUT,
+};
+
+struct rpcif_op {
+	struct {
+		u8 buswidth;
+		u8 opcode;
+		bool ddr;
+	} cmd, ocmd;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+		bool ddr;
+		u64 val;
+	} addr;
+
+	struct {
+		u8 ncycles;
+		u8 buswidth;
+	} dummy;
+
+	struct {
+		u8 nbytes;
+		u8 buswidth;
+		bool ddr;
+		u32 val;
+	} option;
+
+	struct {
+		u8 buswidth;
+		unsigned int nbytes;
+		enum rpcif_data_dir dir;
+		bool ddr;
+		union {
+			void *in;
+			const void *out;
+		} buf;
+	} data;
+};
+
+enum rpcif_type {
+	RPCIF_RCAR_GEN3,
+	RPCIF_RCAR_GEN4,
+	RPCIF_RZ_G2L,
+	XSPI_RZ_G3E,
+};
+
+struct rpcif {
+	struct device *dev;
+	void __iomem *dirmap;
+	size_t size;
+	bool xspi;
+};
+
+int rpcif_sw_init(struct rpcif *rpc, struct device *dev);
+int rpcif_hw_init(struct device *dev, bool hyperflash);
+void rpcif_prepare(struct device *dev, const struct rpcif_op *op, u64 *offs,
+		   size_t *len);
+int rpcif_manual_xfer(struct device *dev);
+ssize_t rpcif_dirmap_read(struct device *dev, u64 offs, size_t len, void *buf);
+ssize_t xspi_dirmap_write(struct device *dev, u64 offs, size_t len,
+			  const void *buf);
+
+#endif // __RENESAS_RPC_IF_H