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, 242 insertions, 0 deletions

diff --git a/drivers/mtd/maps/physmap-versatile.c b/drivers/mtd/maps/physmap-versatile.c
new file mode 100644
index 000000000..2e779111b
--- /dev/null
+++ b/drivers/mtd/maps/physmap-versatile.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Versatile OF physmap driver add-on
+ *
+ * Copyright (c) 2016, Linaro Limited
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ */
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/mtd/map.h>
+#include <linux/mfd/syscon.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/bitops.h>
+#include "physmap-versatile.h"
+
+static struct regmap *syscon_regmap;
+
+enum versatile_flashprot {
+	INTEGRATOR_AP_FLASHPROT,
+	INTEGRATOR_CP_FLASHPROT,
+	VERSATILE_FLASHPROT,
+	REALVIEW_FLASHPROT,
+};
+
+static const struct of_device_id syscon_match[] = {
+	{
+		.compatible = "arm,integrator-ap-syscon",
+		.data = (void *)INTEGRATOR_AP_FLASHPROT,
+	},
+	{
+		.compatible = "arm,integrator-cp-syscon",
+		.data = (void *)INTEGRATOR_CP_FLASHPROT,
+	},
+	{
+		.compatible = "arm,core-module-versatile",
+		.data = (void *)VERSATILE_FLASHPROT,
+	},
+	{
+		.compatible = "arm,realview-eb-syscon",
+		.data = (void *)REALVIEW_FLASHPROT,
+	},
+	{
+		.compatible = "arm,realview-pb1176-syscon",
+		.data = (void *)REALVIEW_FLASHPROT,
+	},
+	{
+		.compatible = "arm,realview-pb11mp-syscon",
+		.data = (void *)REALVIEW_FLASHPROT,
+	},
+	{
+		.compatible = "arm,realview-pba8-syscon",
+		.data = (void *)REALVIEW_FLASHPROT,
+	},
+	{
+		.compatible = "arm,realview-pbx-syscon",
+		.data = (void *)REALVIEW_FLASHPROT,
+	},
+	{},
+};
+
+/*
+ * Flash protection handling for the Integrator/AP
+ */
+#define INTEGRATOR_SC_CTRLS_OFFSET	0x08
+#define INTEGRATOR_SC_CTRLC_OFFSET	0x0C
+#define INTEGRATOR_SC_CTRL_FLVPPEN	BIT(1)
+#define INTEGRATOR_SC_CTRL_FLWP		BIT(2)
+
+#define INTEGRATOR_EBI_CSR1_OFFSET	0x04
+/* The manual says bit 2, the code says bit 3, trust the code */
+#define INTEGRATOR_EBI_WRITE_ENABLE	BIT(3)
+#define INTEGRATOR_EBI_LOCK_OFFSET	0x20
+#define INTEGRATOR_EBI_LOCK_VAL		0xA05F
+
+static const struct of_device_id ebi_match[] = {
+	{ .compatible = "arm,external-bus-interface"},
+	{ },
+};
+
+static int ap_flash_init(struct platform_device *pdev)
+{
+	struct device_node *ebi;
+	void __iomem *ebi_base;
+	u32 val;
+	int ret;
+
+	/* Look up the EBI */
+	ebi = of_find_matching_node(NULL, ebi_match);
+	if (!ebi) {
+		return -ENODEV;
+	}
+	ebi_base = of_iomap(ebi, 0);
+	of_node_put(ebi);
+	if (!ebi_base)
+		return -ENODEV;
+
+	/* Clear VPP and write protection bits */
+	ret = regmap_write(syscon_regmap,
+		INTEGRATOR_SC_CTRLC_OFFSET,
+		INTEGRATOR_SC_CTRL_FLVPPEN | INTEGRATOR_SC_CTRL_FLWP);
+	if (ret)
+		dev_err(&pdev->dev, "error clearing Integrator VPP/WP\n");
+
+	/* Unlock the EBI */
+	writel(INTEGRATOR_EBI_LOCK_VAL, ebi_base + INTEGRATOR_EBI_LOCK_OFFSET);
+
+	/* Enable write cycles on the EBI, CSR1 (flash) */
+	val = readl(ebi_base + INTEGRATOR_EBI_CSR1_OFFSET);
+	val |= INTEGRATOR_EBI_WRITE_ENABLE;
+	writel(val, ebi_base + INTEGRATOR_EBI_CSR1_OFFSET);
+
+	/* Lock the EBI again */
+	writel(0, ebi_base + INTEGRATOR_EBI_LOCK_OFFSET);
+	iounmap(ebi_base);
+
+	return 0;
+}
+
+static void ap_flash_set_vpp(struct map_info *map, int on)
+{
+	int ret;
+
+	if (on) {
+		ret = regmap_write(syscon_regmap,
+			INTEGRATOR_SC_CTRLS_OFFSET,
+			INTEGRATOR_SC_CTRL_FLVPPEN | INTEGRATOR_SC_CTRL_FLWP);
+		if (ret)
+			pr_err("error enabling AP VPP\n");
+	} else {
+		ret = regmap_write(syscon_regmap,
+			INTEGRATOR_SC_CTRLC_OFFSET,
+			INTEGRATOR_SC_CTRL_FLVPPEN | INTEGRATOR_SC_CTRL_FLWP);
+		if (ret)
+			pr_err("error disabling AP VPP\n");
+	}
+}
+
+/*
+ * Flash protection handling for the Integrator/CP
+ */
+
+#define INTCP_FLASHPROG_OFFSET		0x04
+#define CINTEGRATOR_FLVPPEN		BIT(0)
+#define CINTEGRATOR_FLWREN		BIT(1)
+#define CINTEGRATOR_FLMASK		BIT(0)|BIT(1)
+
+static void cp_flash_set_vpp(struct map_info *map, int on)
+{
+	int ret;
+
+	if (on) {
+		ret = regmap_update_bits(syscon_regmap,
+				INTCP_FLASHPROG_OFFSET,
+				CINTEGRATOR_FLMASK,
+				CINTEGRATOR_FLVPPEN | CINTEGRATOR_FLWREN);
+		if (ret)
+			pr_err("error setting CP VPP\n");
+	} else {
+		ret = regmap_update_bits(syscon_regmap,
+				INTCP_FLASHPROG_OFFSET,
+				CINTEGRATOR_FLMASK,
+				0);
+		if (ret)
+			pr_err("error setting CP VPP\n");
+	}
+}
+
+/*
+ * Flash protection handling for the Versatiles and RealViews
+ */
+
+#define VERSATILE_SYS_FLASH_OFFSET            0x4C
+
+static void versatile_flash_set_vpp(struct map_info *map, int on)
+{
+	int ret;
+
+	ret = regmap_update_bits(syscon_regmap, VERSATILE_SYS_FLASH_OFFSET,
+				 0x01, !!on);
+	if (ret)
+		pr_err("error setting Versatile VPP\n");
+}
+
+int of_flash_probe_versatile(struct platform_device *pdev,
+			     struct device_node *np,
+			     struct map_info *map)
+{
+	struct device_node *sysnp;
+	const struct of_device_id *devid;
+	struct regmap *rmap;
+	static enum versatile_flashprot versatile_flashprot;
+	int ret;
+
+	/* Not all flash chips use this protection line */
+	if (!of_device_is_compatible(np, "arm,versatile-flash"))
+		return 0;
+
+	/* For first chip probed, look up the syscon regmap */
+	if (!syscon_regmap) {
+		sysnp = of_find_matching_node_and_match(NULL,
+							syscon_match,
+							&devid);
+		if (!sysnp)
+			return -ENODEV;
+
+		versatile_flashprot = (uintptr_t)devid->data;
+		rmap = syscon_node_to_regmap(sysnp);
+		of_node_put(sysnp);
+		if (IS_ERR(rmap))
+			return PTR_ERR(rmap);
+
+		syscon_regmap = rmap;
+	}
+
+	switch (versatile_flashprot) {
+	case INTEGRATOR_AP_FLASHPROT:
+		ret = ap_flash_init(pdev);
+		if (ret)
+			return ret;
+		map->set_vpp = ap_flash_set_vpp;
+		dev_info(&pdev->dev, "Integrator/AP flash protection\n");
+		break;
+	case INTEGRATOR_CP_FLASHPROT:
+		map->set_vpp = cp_flash_set_vpp;
+		dev_info(&pdev->dev, "Integrator/CP flash protection\n");
+		break;
+	case VERSATILE_FLASHPROT:
+	case REALVIEW_FLASHPROT:
+		map->set_vpp = versatile_flash_set_vpp;
+		dev_info(&pdev->dev, "versatile/realview flash protection\n");
+		break;
+	default:
+		dev_info(&pdev->dev, "device marked as Versatile flash "
+			 "but no system controller was found\n");
+		break;
+	}
+
+	return 0;
+}