x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

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);