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, 225 insertions, 0 deletions

diff --git a/drivers/edac/a72_edac.c b/drivers/edac/a72_edac.c
new file mode 100644
index 000000000..9262d75c3
--- /dev/null
+++ b/drivers/edac/a72_edac.c
@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Cortex A72 EDAC L1 and L2 cache error detection
+ *
+ * Copyright (c) 2020 Pengutronix, Sascha Hauer <s.hauer@pengutronix.de>
+ * Copyright (c) 2025 Microsoft Corporation, <vijayb@linux.microsoft.com>
+ *
+ * Based on Code from:
+ * Copyright (c) 2018, NXP Semiconductor
+ * Author: York Sun <york.sun@nxp.com>
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/bitfield.h>
+#include <asm/smp_plat.h>
+
+#include "edac_module.h"
+
+#define DRVNAME			"a72-edac"
+
+#define SYS_CPUMERRSR_EL1	sys_reg(3, 1, 15, 2, 2)
+#define SYS_L2MERRSR_EL1	sys_reg(3, 1, 15, 2, 3)
+
+#define CPUMERRSR_EL1_RAMID	GENMASK(30, 24)
+#define L2MERRSR_EL1_CPUID_WAY	GENMASK(21, 18)
+
+#define CPUMERRSR_EL1_VALID	BIT(31)
+#define CPUMERRSR_EL1_FATAL	BIT(63)
+#define L2MERRSR_EL1_VALID	BIT(31)
+#define L2MERRSR_EL1_FATAL	BIT(63)
+
+#define L1_I_TAG_RAM		0x00
+#define L1_I_DATA_RAM		0x01
+#define L1_D_TAG_RAM		0x08
+#define L1_D_DATA_RAM		0x09
+#define TLB_RAM			0x18
+
+#define MESSAGE_SIZE		64
+
+struct mem_err_synd_reg {
+	u64 cpu_mesr;
+	u64 l2_mesr;
+};
+
+static struct cpumask compat_mask;
+
+static void report_errors(struct edac_device_ctl_info *edac_ctl, int cpu,
+			  struct mem_err_synd_reg *mesr)
+{
+	u64 cpu_mesr = mesr->cpu_mesr;
+	u64 l2_mesr = mesr->l2_mesr;
+	char msg[MESSAGE_SIZE];
+
+	if (cpu_mesr & CPUMERRSR_EL1_VALID) {
+		const char *str;
+		bool fatal = cpu_mesr & CPUMERRSR_EL1_FATAL;
+
+		switch (FIELD_GET(CPUMERRSR_EL1_RAMID, cpu_mesr)) {
+		case L1_I_TAG_RAM:
+			str = "L1-I Tag RAM";
+			break;
+		case L1_I_DATA_RAM:
+			str = "L1-I Data RAM";
+			break;
+		case L1_D_TAG_RAM:
+			str = "L1-D Tag RAM";
+			break;
+		case L1_D_DATA_RAM:
+			str = "L1-D Data RAM";
+			break;
+		case TLB_RAM:
+			str = "TLB RAM";
+			break;
+		default:
+			str = "Unspecified";
+			break;
+		}
+
+		snprintf(msg, MESSAGE_SIZE, "%s %s error(s) on CPU %d",
+			 str, fatal ? "fatal" : "correctable", cpu);
+
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 0, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 0, msg);
+	}
+
+	if (l2_mesr & L2MERRSR_EL1_VALID) {
+		bool fatal = l2_mesr & L2MERRSR_EL1_FATAL;
+
+		snprintf(msg, MESSAGE_SIZE, "L2 %s error(s) on CPU %d CPUID/WAY 0x%lx",
+			 fatal ? "fatal" : "correctable", cpu,
+			 FIELD_GET(L2MERRSR_EL1_CPUID_WAY, l2_mesr));
+		if (fatal)
+			edac_device_handle_ue(edac_ctl, cpu, 1, msg);
+		else
+			edac_device_handle_ce(edac_ctl, cpu, 1, msg);
+	}
+}
+
+static void read_errors(void *data)
+{
+	struct mem_err_synd_reg *mesr = data;
+
+	mesr->cpu_mesr = read_sysreg_s(SYS_CPUMERRSR_EL1);
+	if (mesr->cpu_mesr & CPUMERRSR_EL1_VALID) {
+		write_sysreg_s(0, SYS_CPUMERRSR_EL1);
+		isb();
+	}
+	mesr->l2_mesr = read_sysreg_s(SYS_L2MERRSR_EL1);
+	if (mesr->l2_mesr & L2MERRSR_EL1_VALID) {
+		write_sysreg_s(0, SYS_L2MERRSR_EL1);
+		isb();
+	}
+}
+
+static void a72_edac_check(struct edac_device_ctl_info *edac_ctl)
+{
+	struct mem_err_synd_reg mesr;
+	int cpu;
+
+	cpus_read_lock();
+	for_each_cpu_and(cpu, cpu_online_mask, &compat_mask) {
+		smp_call_function_single(cpu, read_errors, &mesr, true);
+		report_errors(edac_ctl, cpu, &mesr);
+	}
+	cpus_read_unlock();
+}
+
+static int a72_edac_probe(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl;
+	struct device *dev = &pdev->dev;
+	int rc;
+
+	edac_ctl = edac_device_alloc_ctl_info(0, "cpu",
+					      num_possible_cpus(), "L", 2, 1,
+					      edac_device_alloc_index());
+	if (!edac_ctl)
+		return -ENOMEM;
+
+	edac_ctl->edac_check = a72_edac_check;
+	edac_ctl->dev = dev;
+	edac_ctl->mod_name = dev_name(dev);
+	edac_ctl->dev_name = dev_name(dev);
+	edac_ctl->ctl_name = DRVNAME;
+	dev_set_drvdata(dev, edac_ctl);
+
+	rc = edac_device_add_device(edac_ctl);
+	if (rc)
+		goto out_dev;
+
+	return 0;
+
+out_dev:
+	edac_device_free_ctl_info(edac_ctl);
+
+	return rc;
+}
+
+static void a72_edac_remove(struct platform_device *pdev)
+{
+	struct edac_device_ctl_info *edac_ctl = dev_get_drvdata(&pdev->dev);
+
+	edac_device_del_device(edac_ctl->dev);
+	edac_device_free_ctl_info(edac_ctl);
+}
+
+static const struct of_device_id cortex_arm64_edac_of_match[] = {
+	{ .compatible = "arm,cortex-a72" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, cortex_arm64_edac_of_match);
+
+static struct platform_driver a72_edac_driver = {
+	.probe = a72_edac_probe,
+	.remove = a72_edac_remove,
+	.driver = {
+		.name = DRVNAME,
+	},
+};
+
+static struct platform_device *a72_pdev;
+
+static int __init a72_edac_driver_init(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		struct device_node *np __free(device_node) = of_cpu_device_node_get(cpu);
+		if (np) {
+			if (of_match_node(cortex_arm64_edac_of_match, np) &&
+			    of_property_read_bool(np, "edac-enabled")) {
+				cpumask_set_cpu(cpu, &compat_mask);
+			}
+		} else {
+			pr_warn("failed to find device node for CPU %d\n", cpu);
+		}
+	}
+
+	if (cpumask_empty(&compat_mask))
+		return 0;
+
+	a72_pdev = platform_device_register_simple(DRVNAME, -1, NULL, 0);
+	if (IS_ERR(a72_pdev)) {
+		pr_err("failed to register A72 EDAC device\n");
+		return PTR_ERR(a72_pdev);
+	}
+
+	return platform_driver_register(&a72_edac_driver);
+}
+
+static void __exit a72_edac_driver_exit(void)
+{
+	platform_device_unregister(a72_pdev);
+	platform_driver_unregister(&a72_edac_driver);
+}
+
+module_init(a72_edac_driver_init);
+module_exit(a72_edac_driver_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("Cortex A72 L1 and L2 cache EDAC driver");