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/hwmon/surface_temp.c | 235 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 235 insertions(+) create mode 100644 drivers/hwmon/surface_temp.c (limited to 'drivers/hwmon/surface_temp.c') diff --git a/drivers/hwmon/surface_temp.c b/drivers/hwmon/surface_temp.c new file mode 100644 index 000000000..cd21f331f --- /dev/null +++ b/drivers/hwmon/surface_temp.c @@ -0,0 +1,235 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM). + * + * Copyright (C) 2022-2023 Maximilian Luz + */ + +#include +#include +#include +#include +#include + +#include +#include + +/* -- SAM interface. -------------------------------------------------------- */ + +/* + * Available sensors are indicated by a 16-bit bitfield, where a 1 marks the + * presence of a sensor. So we have at most 16 possible sensors/channels. + */ +#define SSAM_TMP_SENSOR_MAX_COUNT 16 + +/* + * All names observed so far are 6 characters long, but there's only + * zeros after the name, so perhaps they can be longer. This number reflects + * the maximum zero-padded space observed in the returned buffer. + */ +#define SSAM_TMP_SENSOR_NAME_LENGTH 18 + +struct ssam_tmp_get_name_rsp { + __le16 unknown1; + char unknown2; + char name[SSAM_TMP_SENSOR_NAME_LENGTH]; +} __packed; + +static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21); + +SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, { + .target_category = SSAM_SSH_TC_TMP, + .command_id = 0x04, +}); + +SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, { + .target_category = SSAM_SSH_TC_TMP, + .command_id = 0x01, +}); + +SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, { + .target_category = SSAM_SSH_TC_TMP, + .command_id = 0x0e, +}); + +static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors) +{ + __le16 sensors_le; + int status; + + status = __ssam_tmp_get_available_sensors(sdev, &sensors_le); + if (status) + return status; + + *sensors = le16_to_cpu(sensors_le); + return 0; +} + +static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature) +{ + __le16 temp_le; + int status; + + status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le); + if (status) + return status; + + /* Convert 1/10 °K to 1/1000 °C */ + *temperature = (le16_to_cpu(temp_le) - 2731) * 100L; + return 0; +} + +static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len) +{ + struct ssam_tmp_get_name_rsp name_rsp; + int status; + + status = __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp); + if (status) + return status; + + /* + * This should not fail unless the name in the returned struct is not + * null-terminated or someone changed something in the struct + * definitions above, since our buffer and struct have the same + * capacity by design. So if this fails, log an error message. Since + * the more likely cause is that the returned string isn't + * null-terminated, we might have received garbage (as opposed to just + * an incomplete string), so also fail the function. + */ + status = strscpy(buf, name_rsp.name, buf_len); + if (status < 0) { + dev_err(&sdev->dev, "received non-null-terminated sensor name string\n"); + return status; + } + + return 0; +} + +/* -- Driver.---------------------------------------------------------------- */ + +struct ssam_temp { + struct ssam_device *sdev; + s16 sensors; + char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH]; +}; + +static umode_t ssam_temp_hwmon_is_visible(const void *data, + enum hwmon_sensor_types type, + u32 attr, int channel) +{ + const struct ssam_temp *ssam_temp = data; + + if (!(ssam_temp->sensors & BIT(channel))) + return 0; + + return 0444; +} + +static int ssam_temp_hwmon_read(struct device *dev, + enum hwmon_sensor_types type, + u32 attr, int channel, long *value) +{ + const struct ssam_temp *ssam_temp = dev_get_drvdata(dev); + + return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value); +} + +static int ssam_temp_hwmon_read_string(struct device *dev, + enum hwmon_sensor_types type, + u32 attr, int channel, const char **str) +{ + const struct ssam_temp *ssam_temp = dev_get_drvdata(dev); + + *str = ssam_temp->names[channel]; + return 0; +} + +static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = { + HWMON_CHANNEL_INFO(chip, + HWMON_C_REGISTER_TZ), + HWMON_CHANNEL_INFO(temp, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL, + HWMON_T_INPUT | HWMON_T_LABEL), + NULL +}; + +static const struct hwmon_ops ssam_temp_hwmon_ops = { + .is_visible = ssam_temp_hwmon_is_visible, + .read = ssam_temp_hwmon_read, + .read_string = ssam_temp_hwmon_read_string, +}; + +static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = { + .ops = &ssam_temp_hwmon_ops, + .info = ssam_temp_hwmon_info, +}; + +static int ssam_temp_probe(struct ssam_device *sdev) +{ + struct ssam_temp *ssam_temp; + struct device *hwmon_dev; + s16 sensors; + int channel; + int status; + + status = ssam_tmp_get_available_sensors(sdev, &sensors); + if (status) + return status; + + ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL); + if (!ssam_temp) + return -ENOMEM; + + ssam_temp->sdev = sdev; + ssam_temp->sensors = sensors; + + /* Retrieve the name for each available sensor. */ + for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) { + if (!(sensors & BIT(channel))) + continue; + + status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel], + SSAM_TMP_SENSOR_NAME_LENGTH); + if (status) + return status; + } + + hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp, + &ssam_temp_hwmon_chip_info, NULL); + return PTR_ERR_OR_ZERO(hwmon_dev); +} + +static const struct ssam_device_id ssam_temp_match[] = { + { SSAM_SDEV(TMP, SAM, 0x00, 0x02) }, + { }, +}; +MODULE_DEVICE_TABLE(ssam, ssam_temp_match); + +static struct ssam_device_driver ssam_temp = { + .probe = ssam_temp_probe, + .match_table = ssam_temp_match, + .driver = { + .name = "surface_temp", + .probe_type = PROBE_PREFER_ASYNCHRONOUS, + }, +}; +module_ssam_device_driver(ssam_temp); + +MODULE_AUTHOR("Maximilian Luz "); +MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1