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, 202 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-rda.c b/drivers/clocksource/timer-rda.c
new file mode 100644
index 000000000..0be8e0597
--- /dev/null
+++ b/drivers/clocksource/timer-rda.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * RDA8810PL SoC timer driver
+ *
+ * Copyright RDA Microelectronics Company Limited
+ * Copyright (c) 2017 Andreas Färber
+ * Copyright (c) 2018 Manivannan Sadhasivam
+ *
+ * RDA8810PL has two independent timers: OSTIMER (56 bit) and HWTIMER (64 bit).
+ * Each timer provides optional interrupt support. In this driver, OSTIMER is
+ * used for clockevents and HWTIMER is used for clocksource.
+ */
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+
+#include "timer-of.h"
+
+#define RDA_OSTIMER_LOADVAL_L	0x000
+#define RDA_OSTIMER_CTRL	0x004
+#define RDA_HWTIMER_LOCKVAL_L	0x024
+#define RDA_HWTIMER_LOCKVAL_H	0x028
+#define RDA_TIMER_IRQ_MASK_SET	0x02c
+#define RDA_TIMER_IRQ_MASK_CLR	0x030
+#define RDA_TIMER_IRQ_CLR	0x034
+
+#define RDA_OSTIMER_CTRL_ENABLE		BIT(24)
+#define RDA_OSTIMER_CTRL_REPEAT		BIT(28)
+#define RDA_OSTIMER_CTRL_LOAD		BIT(30)
+
+#define RDA_TIMER_IRQ_MASK_OSTIMER	BIT(0)
+
+#define RDA_TIMER_IRQ_CLR_OSTIMER	BIT(0)
+
+static int rda_ostimer_start(void __iomem *base, bool periodic, u64 cycles)
+{
+	u32 ctrl, load_l;
+
+	load_l = (u32)cycles;
+	ctrl = ((cycles >> 32) & 0xffffff);
+	ctrl |= RDA_OSTIMER_CTRL_LOAD | RDA_OSTIMER_CTRL_ENABLE;
+	if (periodic)
+		ctrl |= RDA_OSTIMER_CTRL_REPEAT;
+
+	/* Enable ostimer interrupt first */
+	writel_relaxed(RDA_TIMER_IRQ_MASK_OSTIMER,
+		       base + RDA_TIMER_IRQ_MASK_SET);
+
+	/* Write low 32 bits first, high 24 bits are with ctrl */
+	writel_relaxed(load_l, base + RDA_OSTIMER_LOADVAL_L);
+	writel_relaxed(ctrl, base + RDA_OSTIMER_CTRL);
+
+	return 0;
+}
+
+static int rda_ostimer_stop(void __iomem *base)
+{
+	/* Disable ostimer interrupt first */
+	writel_relaxed(RDA_TIMER_IRQ_MASK_OSTIMER,
+		       base + RDA_TIMER_IRQ_MASK_CLR);
+
+	writel_relaxed(0, base + RDA_OSTIMER_CTRL);
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_shutdown(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_oneshot(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	return 0;
+}
+
+static int rda_ostimer_set_state_periodic(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+	unsigned long cycles_per_jiffy;
+
+	rda_ostimer_stop(timer_of_base(to));
+
+	cycles_per_jiffy = ((unsigned long long)NSEC_PER_SEC / HZ *
+			     evt->mult) >> evt->shift;
+	rda_ostimer_start(timer_of_base(to), true, cycles_per_jiffy);
+
+	return 0;
+}
+
+static int rda_ostimer_tick_resume(struct clock_event_device *evt)
+{
+	return 0;
+}
+
+static int rda_ostimer_set_next_event(unsigned long evt,
+				      struct clock_event_device *ev)
+{
+	struct timer_of *to = to_timer_of(ev);
+
+	rda_ostimer_start(timer_of_base(to), false, evt);
+
+	return 0;
+}
+
+static irqreturn_t rda_ostimer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+	struct timer_of *to = to_timer_of(evt);
+
+	/* clear timer int */
+	writel_relaxed(RDA_TIMER_IRQ_CLR_OSTIMER,
+		       timer_of_base(to) + RDA_TIMER_IRQ_CLR);
+
+	if (evt->event_handler)
+		evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct timer_of rda_ostimer_of = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_BASE,
+
+	.clkevt = {
+		.name = "rda-ostimer",
+		.rating = 250,
+		.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
+			    CLOCK_EVT_FEAT_DYNIRQ,
+		.set_state_shutdown = rda_ostimer_set_state_shutdown,
+		.set_state_oneshot = rda_ostimer_set_state_oneshot,
+		.set_state_periodic = rda_ostimer_set_state_periodic,
+		.tick_resume = rda_ostimer_tick_resume,
+		.set_next_event	= rda_ostimer_set_next_event,
+	},
+
+	.of_base = {
+		.name = "rda-timer",
+		.index = 0,
+	},
+
+	.of_irq = {
+		.name = "ostimer",
+		.handler = rda_ostimer_interrupt,
+		.flags = IRQF_TIMER,
+	},
+};
+
+static u64 rda_hwtimer_clocksource_read(void)
+{
+	void __iomem *base = timer_of_base(&rda_ostimer_of);
+	u32 lo, hi;
+
+	/* Always read low 32 bits first */
+	do {
+		lo = readl_relaxed(base + RDA_HWTIMER_LOCKVAL_L);
+		hi = readl_relaxed(base + RDA_HWTIMER_LOCKVAL_H);
+	} while (hi != readl_relaxed(base + RDA_HWTIMER_LOCKVAL_H));
+
+	return ((u64)hi << 32) | lo;
+}
+
+static u64 rda_hwtimer_read(struct clocksource *cs)
+{
+	return rda_hwtimer_clocksource_read();
+}
+
+static struct clocksource rda_hwtimer_clocksource = {
+	.name           = "rda-timer",
+	.rating         = 400,
+	.read           = rda_hwtimer_read,
+	.mask           = CLOCKSOURCE_MASK(64),
+	.flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static int __init rda_timer_init(struct device_node *np)
+{
+	unsigned long rate = 2000000;
+	int ret;
+
+	ret = timer_of_init(np, &rda_ostimer_of);
+	if (ret)
+		return ret;
+
+	clocksource_register_hz(&rda_hwtimer_clocksource, rate);
+	sched_clock_register(rda_hwtimer_clocksource_read, 64, rate);
+
+	clockevents_config_and_register(&rda_ostimer_of.clkevt, rate,
+					0x2, UINT_MAX);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(rda8810pl, "rda,8810pl-timer", rda_timer_init);