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, 92 insertions, 0 deletions

diff --git a/drivers/usb/chipidea/trace.h b/drivers/usb/chipidea/trace.h
new file mode 100644
index 000000000..1875419cd
--- /dev/null
+++ b/drivers/usb/chipidea/trace.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Trace support header file for device mode
+ *
+ * Copyright (C) 2020 NXP
+ *
+ * Author: Peter Chen <peter.chen@nxp.com>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM chipidea
+
+#if !defined(__LINUX_CHIPIDEA_TRACE) || defined(TRACE_HEADER_MULTI_READ)
+#define __LINUX_CHIPIDEA_TRACE
+
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+#include <linux/usb/chipidea.h>
+#include "ci.h"
+#include "udc.h"
+
+#define CHIPIDEA_MSG_MAX	500
+
+void ci_log(struct ci_hdrc *ci, const char *fmt, ...);
+
+TRACE_EVENT(ci_log,
+	TP_PROTO(struct ci_hdrc *ci, struct va_format *vaf),
+	TP_ARGS(ci, vaf),
+	TP_STRUCT__entry(
+		__string(name, dev_name(ci->dev))
+		__vstring(msg, vaf->fmt, vaf->va)
+	),
+	TP_fast_assign(
+		__assign_str(name);
+		__assign_vstr(msg, vaf->fmt, vaf->va);
+	),
+	TP_printk("%s: %s", __get_str(name), __get_str(msg))
+);
+
+DECLARE_EVENT_CLASS(ci_log_trb,
+	TP_PROTO(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq, struct td_node *td),
+	TP_ARGS(hwep, hwreq, td),
+	TP_STRUCT__entry(
+		__string(name, hwep->name)
+		__field(struct td_node *, td)
+		__field(struct usb_request *, req)
+		__field(dma_addr_t, dma)
+		__field(s32, td_remaining_size)
+		__field(u32, next)
+		__field(u32, token)
+		__field(u32, type)
+	),
+	TP_fast_assign(
+		__assign_str(name);
+		__entry->req = &hwreq->req;
+		__entry->td = td;
+		__entry->dma = td->dma;
+		__entry->td_remaining_size = td->td_remaining_size;
+		__entry->next = le32_to_cpu(td->ptr->next);
+		__entry->token = le32_to_cpu(td->ptr->token);
+		__entry->type = usb_endpoint_type(hwep->ep.desc);
+	),
+	TP_printk("%s: req: %p, td: %p, td_dma_address: %pad, remaining_size: %d, "
+	       "next: %x, total bytes: %d, status: %lx",
+		__get_str(name), __entry->req, __entry->td, &__entry->dma,
+		__entry->td_remaining_size, __entry->next,
+		(int)((__entry->token & TD_TOTAL_BYTES) >> __ffs(TD_TOTAL_BYTES)),
+		__entry->token & TD_STATUS
+	)
+);
+
+DEFINE_EVENT(ci_log_trb, ci_prepare_td,
+	TP_PROTO(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq, struct td_node *td),
+	TP_ARGS(hwep, hwreq, td)
+);
+
+DEFINE_EVENT(ci_log_trb, ci_complete_td,
+	TP_PROTO(struct ci_hw_ep *hwep, struct ci_hw_req *hwreq, struct td_node *td),
+	TP_ARGS(hwep, hwreq, td)
+);
+
+#endif /* __LINUX_CHIPIDEA_TRACE */
+
+/* this part must be outside header guard */
+
+#undef TRACE_INCLUDE_PATH
+#define TRACE_INCLUDE_PATH .
+
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_FILE trace
+
+#include <trace/define_trace.h>