From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/input/misc/cpcap-pwrbutton.c | 112 +++++++++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) create mode 100644 drivers/input/misc/cpcap-pwrbutton.c (limited to 'drivers/input/misc/cpcap-pwrbutton.c') diff --git a/drivers/input/misc/cpcap-pwrbutton.c b/drivers/input/misc/cpcap-pwrbutton.c new file mode 100644 index 000000000..85cddb847 --- /dev/null +++ b/drivers/input/misc/cpcap-pwrbutton.c @@ -0,0 +1,112 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * CPCAP Power Button Input Driver + * + * Copyright (C) 2017 Sebastian Reichel + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define CPCAP_IRQ_ON 23 +#define CPCAP_IRQ_ON_BITMASK (1 << (CPCAP_IRQ_ON % 16)) + +struct cpcap_power_button { + struct regmap *regmap; + struct input_dev *idev; + struct device *dev; +}; + +static irqreturn_t powerbutton_irq(int irq, void *_button) +{ + struct cpcap_power_button *button = _button; + int val; + + val = cpcap_sense_virq(button->regmap, irq); + if (val < 0) { + dev_err(button->dev, "irq read failed: %d", val); + return IRQ_HANDLED; + } + + pm_wakeup_event(button->dev, 0); + input_report_key(button->idev, KEY_POWER, val); + input_sync(button->idev); + + return IRQ_HANDLED; +} + +static int cpcap_power_button_probe(struct platform_device *pdev) +{ + struct cpcap_power_button *button; + int irq; + int err; + + irq = platform_get_irq(pdev, 0); + if (irq < 0) + return irq; + + button = devm_kmalloc(&pdev->dev, sizeof(*button), GFP_KERNEL); + if (!button) + return -ENOMEM; + + button->idev = devm_input_allocate_device(&pdev->dev); + if (!button->idev) + return -ENOMEM; + + button->regmap = dev_get_regmap(pdev->dev.parent, NULL); + if (!button->regmap) + return -ENODEV; + + button->dev = &pdev->dev; + + button->idev->name = "cpcap-pwrbutton"; + button->idev->phys = "cpcap-pwrbutton/input0"; + input_set_capability(button->idev, EV_KEY, KEY_POWER); + + err = devm_request_threaded_irq(&pdev->dev, irq, NULL, + powerbutton_irq, IRQF_ONESHOT, "cpcap_pwrbutton", button); + if (err < 0) { + dev_err(&pdev->dev, "IRQ request failed: %d\n", err); + return err; + } + + err = input_register_device(button->idev); + if (err) { + dev_err(&pdev->dev, "Input register failed: %d\n", err); + return err; + } + + device_init_wakeup(&pdev->dev, true); + + return 0; +} + +#ifdef CONFIG_OF +static const struct of_device_id cpcap_pwrbutton_dt_match_table[] = { + { .compatible = "motorola,cpcap-pwrbutton" }, + {}, +}; +MODULE_DEVICE_TABLE(of, cpcap_pwrbutton_dt_match_table); +#endif + +static struct platform_driver cpcap_power_button_driver = { + .probe = cpcap_power_button_probe, + .driver = { + .name = "cpcap-pwrbutton", + .of_match_table = of_match_ptr(cpcap_pwrbutton_dt_match_table), + }, +}; +module_platform_driver(cpcap_power_button_driver); + +MODULE_ALIAS("platform:cpcap-pwrbutton"); +MODULE_DESCRIPTION("CPCAP Power Button"); +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Sebastian Reichel "); -- cgit v1.3.1