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, 183 insertions, 0 deletions

diff --git a/drivers/clocksource/ingenic-ost.c b/drivers/clocksource/ingenic-ost.c
new file mode 100644
index 000000000..e0ec33307
--- /dev/null
+++ b/drivers/clocksource/ingenic-ost.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * JZ47xx SoCs TCU Operating System Timer driver
+ *
+ * Copyright (C) 2016 Maarten ter Huurne <maarten@treewalker.org>
+ * Copyright (C) 2020 Paul Cercueil <paul@crapouillou.net>
+ */
+
+#include <linux/clk.h>
+#include <linux/clocksource.h>
+#include <linux/mfd/ingenic-tcu.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pm.h>
+#include <linux/regmap.h>
+#include <linux/sched_clock.h>
+
+#define TCU_OST_TCSR_MASK	0xffc0
+#define TCU_OST_TCSR_CNT_MD	BIT(15)
+
+#define TCU_OST_CHANNEL		15
+
+/*
+ * The TCU_REG_OST_CNT{L,R} from <linux/mfd/ingenic-tcu.h> are only for the
+ * regmap; these are for use with the __iomem pointer.
+ */
+#define OST_REG_CNTL		0x4
+#define OST_REG_CNTH		0x8
+
+struct ingenic_ost_soc_info {
+	bool is64bit;
+};
+
+struct ingenic_ost {
+	void __iomem *regs;
+	struct clk *clk;
+
+	struct clocksource cs;
+};
+
+static struct ingenic_ost *ingenic_ost;
+
+static u64 notrace ingenic_ost_read_cntl(void)
+{
+	/* Read using __iomem pointer instead of regmap to avoid locking */
+	return readl(ingenic_ost->regs + OST_REG_CNTL);
+}
+
+static u64 notrace ingenic_ost_read_cnth(void)
+{
+	/* Read using __iomem pointer instead of regmap to avoid locking */
+	return readl(ingenic_ost->regs + OST_REG_CNTH);
+}
+
+static u64 notrace ingenic_ost_clocksource_readl(struct clocksource *cs)
+{
+	return ingenic_ost_read_cntl();
+}
+
+static u64 notrace ingenic_ost_clocksource_readh(struct clocksource *cs)
+{
+	return ingenic_ost_read_cnth();
+}
+
+static int __init ingenic_ost_probe(struct platform_device *pdev)
+{
+	const struct ingenic_ost_soc_info *soc_info;
+	struct device *dev = &pdev->dev;
+	struct ingenic_ost *ost;
+	struct clocksource *cs;
+	struct regmap *map;
+	unsigned long rate;
+	int err;
+
+	soc_info = device_get_match_data(dev);
+	if (!soc_info)
+		return -EINVAL;
+
+	ost = devm_kzalloc(dev, sizeof(*ost), GFP_KERNEL);
+	if (!ost)
+		return -ENOMEM;
+
+	ingenic_ost = ost;
+
+	ost->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ost->regs))
+		return PTR_ERR(ost->regs);
+
+	map = device_node_to_regmap(dev->parent->of_node);
+	if (IS_ERR(map)) {
+		dev_err(dev, "regmap not found");
+		return PTR_ERR(map);
+	}
+
+	ost->clk = devm_clk_get_enabled(dev, "ost");
+	if (IS_ERR(ost->clk))
+		return PTR_ERR(ost->clk);
+
+	/* Clear counter high/low registers */
+	if (soc_info->is64bit)
+		regmap_write(map, TCU_REG_OST_CNTL, 0);
+	regmap_write(map, TCU_REG_OST_CNTH, 0);
+
+	/* Don't reset counter at compare value. */
+	regmap_update_bits(map, TCU_REG_OST_TCSR,
+			   TCU_OST_TCSR_MASK, TCU_OST_TCSR_CNT_MD);
+
+	rate = clk_get_rate(ost->clk);
+
+	/* Enable OST TCU channel */
+	regmap_write(map, TCU_REG_TESR, BIT(TCU_OST_CHANNEL));
+
+	cs = &ost->cs;
+	cs->name	= "ingenic-ost";
+	cs->rating	= 320;
+	cs->flags	= CLOCK_SOURCE_IS_CONTINUOUS;
+	cs->mask	= CLOCKSOURCE_MASK(32);
+
+	if (soc_info->is64bit)
+		cs->read = ingenic_ost_clocksource_readl;
+	else
+		cs->read = ingenic_ost_clocksource_readh;
+
+	err = clocksource_register_hz(cs, rate);
+	if (err) {
+		dev_err(dev, "clocksource registration failed");
+		return err;
+	}
+
+	if (soc_info->is64bit)
+		sched_clock_register(ingenic_ost_read_cntl, 32, rate);
+	else
+		sched_clock_register(ingenic_ost_read_cnth, 32, rate);
+
+	return 0;
+}
+
+static int ingenic_ost_suspend(struct device *dev)
+{
+	struct ingenic_ost *ost = dev_get_drvdata(dev);
+
+	clk_disable(ost->clk);
+
+	return 0;
+}
+
+static int ingenic_ost_resume(struct device *dev)
+{
+	struct ingenic_ost *ost = dev_get_drvdata(dev);
+
+	return clk_enable(ost->clk);
+}
+
+static const struct dev_pm_ops ingenic_ost_pm_ops = {
+	/* _noirq: We want the OST clock to be gated last / ungated first */
+	.suspend_noirq = ingenic_ost_suspend,
+	.resume_noirq  = ingenic_ost_resume,
+};
+
+static const struct ingenic_ost_soc_info jz4725b_ost_soc_info = {
+	.is64bit = false,
+};
+
+static const struct ingenic_ost_soc_info jz4760b_ost_soc_info = {
+	.is64bit = true,
+};
+
+static const struct of_device_id ingenic_ost_of_match[] = {
+	{ .compatible = "ingenic,jz4725b-ost", .data = &jz4725b_ost_soc_info, },
+	{ .compatible = "ingenic,jz4760b-ost", .data = &jz4760b_ost_soc_info, },
+	{ .compatible = "ingenic,jz4770-ost", .data = &jz4760b_ost_soc_info, },
+	{ }
+};
+
+static struct platform_driver ingenic_ost_driver = {
+	.driver = {
+		.name = "ingenic-ost",
+		.pm = pm_sleep_ptr(&ingenic_ost_pm_ops),
+		.of_match_table = ingenic_ost_of_match,
+	},
+};
+builtin_platform_driver_probe(ingenic_ost_driver, ingenic_ost_probe);