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, 226 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-sun4i.c b/drivers/clocksource/timer-sun4i.c
new file mode 100644
index 000000000..c2d04ab7c
--- /dev/null
+++ b/drivers/clocksource/timer-sun4i.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Allwinner A1X SoCs timer handling.
+ *
+ * Copyright (C) 2012 Maxime Ripard
+ *
+ * Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * Based on code from
+ * Allwinner Technology Co., Ltd. <www.allwinnertech.com>
+ * Benn Huang <benn@allwinnertech.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqreturn.h>
+#include <linux/sched_clock.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+#include "timer-of.h"
+
+#define TIMER_IRQ_EN_REG	0x00
+#define TIMER_IRQ_EN(val)		BIT(val)
+#define TIMER_IRQ_ST_REG	0x04
+#define TIMER_IRQ_CLEAR(val)		BIT(val)
+#define TIMER_CTL_REG(val)	(0x10 * val + 0x10)
+#define TIMER_CTL_ENABLE		BIT(0)
+#define TIMER_CTL_RELOAD		BIT(1)
+#define TIMER_CTL_CLK_SRC(val)		(((val) & 0x3) << 2)
+#define TIMER_CTL_CLK_SRC_OSC24M		(1)
+#define TIMER_CTL_CLK_PRES(val)		(((val) & 0x7) << 4)
+#define TIMER_CTL_ONESHOT		BIT(7)
+#define TIMER_INTVAL_REG(val)	(0x10 * (val) + 0x14)
+#define TIMER_CNTVAL_REG(val)	(0x10 * (val) + 0x18)
+
+#define TIMER_SYNC_TICKS	3
+
+/*
+ * When we disable a timer, we need to wait at least for 2 cycles of
+ * the timer source clock. We will use for that the clocksource timer
+ * that is already setup and runs at the same frequency than the other
+ * timers, and we never will be disabled.
+ */
+static void sun4i_clkevt_sync(void __iomem *base)
+{
+	u32 old = readl(base + TIMER_CNTVAL_REG(1));
+
+	while ((old - readl(base + TIMER_CNTVAL_REG(1))) < TIMER_SYNC_TICKS)
+		cpu_relax();
+}
+
+static void sun4i_clkevt_time_stop(void __iomem *base, u8 timer)
+{
+	u32 val = readl(base + TIMER_CTL_REG(timer));
+	writel(val & ~TIMER_CTL_ENABLE, base + TIMER_CTL_REG(timer));
+	sun4i_clkevt_sync(base);
+}
+
+static void sun4i_clkevt_time_setup(void __iomem *base, u8 timer,
+				    unsigned long delay)
+{
+	writel(delay, base + TIMER_INTVAL_REG(timer));
+}
+
+static void sun4i_clkevt_time_start(void __iomem *base, u8 timer,
+				    bool periodic)
+{
+	u32 val = readl(base + TIMER_CTL_REG(timer));
+
+	if (periodic)
+		val &= ~TIMER_CTL_ONESHOT;
+	else
+		val |= TIMER_CTL_ONESHOT;
+
+	writel(val | TIMER_CTL_ENABLE | TIMER_CTL_RELOAD,
+	       base + TIMER_CTL_REG(timer));
+}
+
+static int sun4i_clkevt_shutdown(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	sun4i_clkevt_time_stop(timer_of_base(to), 0);
+
+	return 0;
+}
+
+static int sun4i_clkevt_set_oneshot(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	sun4i_clkevt_time_stop(timer_of_base(to), 0);
+	sun4i_clkevt_time_start(timer_of_base(to), 0, false);
+
+	return 0;
+}
+
+static int sun4i_clkevt_set_periodic(struct clock_event_device *evt)
+{
+	struct timer_of *to = to_timer_of(evt);
+
+	sun4i_clkevt_time_stop(timer_of_base(to), 0);
+	sun4i_clkevt_time_setup(timer_of_base(to), 0, timer_of_period(to));
+	sun4i_clkevt_time_start(timer_of_base(to), 0, true);
+
+	return 0;
+}
+
+static int sun4i_clkevt_next_event(unsigned long evt,
+				   struct clock_event_device *clkevt)
+{
+	struct timer_of *to = to_timer_of(clkevt);
+
+	sun4i_clkevt_time_stop(timer_of_base(to), 0);
+	sun4i_clkevt_time_setup(timer_of_base(to), 0, evt - TIMER_SYNC_TICKS);
+	sun4i_clkevt_time_start(timer_of_base(to), 0, false);
+
+	return 0;
+}
+
+static void sun4i_timer_clear_interrupt(void __iomem *base)
+{
+	writel(TIMER_IRQ_CLEAR(0), base + TIMER_IRQ_ST_REG);
+}
+
+static irqreturn_t sun4i_timer_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *evt = dev_id;
+	struct timer_of *to = to_timer_of(evt);
+
+	sun4i_timer_clear_interrupt(timer_of_base(to));
+	evt->event_handler(evt);
+
+	return IRQ_HANDLED;
+}
+
+static struct timer_of to = {
+	.flags = TIMER_OF_IRQ | TIMER_OF_CLOCK | TIMER_OF_BASE,
+
+	.clkevt = {
+		.name = "sun4i_tick",
+		.rating = 350,
+		.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
+				CLOCK_EVT_FEAT_DYNIRQ,
+		.set_state_shutdown = sun4i_clkevt_shutdown,
+		.set_state_periodic = sun4i_clkevt_set_periodic,
+		.set_state_oneshot = sun4i_clkevt_set_oneshot,
+		.tick_resume = sun4i_clkevt_shutdown,
+		.set_next_event = sun4i_clkevt_next_event,
+		.cpumask = cpu_possible_mask,
+	},
+
+	.of_irq = {
+		.handler = sun4i_timer_interrupt,
+		.flags = IRQF_TIMER | IRQF_IRQPOLL,
+	},
+};
+
+static u64 notrace sun4i_timer_sched_read(void)
+{
+	return ~readl(timer_of_base(&to) + TIMER_CNTVAL_REG(1));
+}
+
+static int __init sun4i_timer_init(struct device_node *node)
+{
+	int ret;
+	u32 val;
+
+	ret = timer_of_init(node, &to);
+	if (ret)
+		return ret;
+
+	writel(~0, timer_of_base(&to) + TIMER_INTVAL_REG(1));
+	writel(TIMER_CTL_ENABLE | TIMER_CTL_RELOAD |
+	       TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
+	       timer_of_base(&to) + TIMER_CTL_REG(1));
+
+	/*
+	 * sched_clock_register does not have priorities, and on sun6i and
+	 * later there is a better sched_clock registered by arm_arch_timer.c
+	 */
+	if (of_machine_is_compatible("allwinner,sun4i-a10") ||
+	    of_machine_is_compatible("allwinner,sun5i-a13") ||
+	    of_machine_is_compatible("allwinner,sun5i-a10s") ||
+	    of_machine_is_compatible("allwinner,suniv-f1c100s"))
+		sched_clock_register(sun4i_timer_sched_read, 32,
+				     timer_of_rate(&to));
+
+	ret = clocksource_mmio_init(timer_of_base(&to) + TIMER_CNTVAL_REG(1),
+				    node->name, timer_of_rate(&to), 350, 32,
+				    clocksource_mmio_readl_down);
+	if (ret) {
+		pr_err("Failed to register clocksource\n");
+		return ret;
+	}
+
+	writel(TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
+	       timer_of_base(&to) + TIMER_CTL_REG(0));
+
+	/* Make sure timer is stopped before playing with interrupts */
+	sun4i_clkevt_time_stop(timer_of_base(&to), 0);
+
+	/* clear timer0 interrupt */
+	sun4i_timer_clear_interrupt(timer_of_base(&to));
+
+	clockevents_config_and_register(&to.clkevt, timer_of_rate(&to),
+					TIMER_SYNC_TICKS + 1, 0xffffffff);
+
+	/* Enable timer0 interrupt */
+	val = readl(timer_of_base(&to) + TIMER_IRQ_EN_REG);
+	writel(val | TIMER_IRQ_EN(0), timer_of_base(&to) + TIMER_IRQ_EN_REG);
+
+	return ret;
+}
+TIMER_OF_DECLARE(sun4i, "allwinner,sun4i-a10-timer",
+		       sun4i_timer_init);
+TIMER_OF_DECLARE(sun8i_a23, "allwinner,sun8i-a23-timer",
+		 sun4i_timer_init);
+TIMER_OF_DECLARE(sun8i_v3s, "allwinner,sun8i-v3s-timer",
+		 sun4i_timer_init);
+TIMER_OF_DECLARE(suniv, "allwinner,suniv-f1c100s-timer",
+		       sun4i_timer_init);