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/tests/.kunitconfig | 3 + drivers/input/tests/Makefile | 3 + drivers/input/tests/input_test.c | 183 +++++++++++++++++++++++++++++++++++++++ 3 files changed, 189 insertions(+) create mode 100644 drivers/input/tests/.kunitconfig create mode 100644 drivers/input/tests/Makefile create mode 100644 drivers/input/tests/input_test.c (limited to 'drivers/input/tests') diff --git a/drivers/input/tests/.kunitconfig b/drivers/input/tests/.kunitconfig new file mode 100644 index 000000000..2f5bedf80 --- /dev/null +++ b/drivers/input/tests/.kunitconfig @@ -0,0 +1,3 @@ +CONFIG_KUNIT=y +CONFIG_INPUT=y +CONFIG_INPUT_KUNIT_TEST=y diff --git a/drivers/input/tests/Makefile b/drivers/input/tests/Makefile new file mode 100644 index 000000000..90cf95418 --- /dev/null +++ b/drivers/input/tests/Makefile @@ -0,0 +1,3 @@ +# SPDX-License-Identifier: GPL-2.0 + +obj-$(CONFIG_INPUT_KUNIT_TEST) += input_test.o diff --git a/drivers/input/tests/input_test.c b/drivers/input/tests/input_test.c new file mode 100644 index 000000000..e105ce71a --- /dev/null +++ b/drivers/input/tests/input_test.c @@ -0,0 +1,183 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * KUnit test for the input core. + * + * Copyright (c) 2023 Red Hat Inc + */ + +#include +#include + +#include + +#define POLL_INTERVAL 100 + +static int input_test_init(struct kunit *test) +{ + struct input_dev *input_dev; + int ret; + + input_dev = input_allocate_device(); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, input_dev); + + input_dev->name = "Test input device"; + input_dev->id.bustype = BUS_VIRTUAL; + input_dev->id.vendor = 1; + input_dev->id.product = 1; + input_dev->id.version = 1; + input_set_capability(input_dev, EV_KEY, BTN_LEFT); + input_set_capability(input_dev, EV_KEY, BTN_RIGHT); + + ret = input_register_device(input_dev); + if (ret) { + input_free_device(input_dev); + KUNIT_FAIL_AND_ABORT(test, "Register device failed: %d", ret); + } + + test->priv = input_dev; + + return 0; +} + +static void input_test_exit(struct kunit *test) +{ + struct input_dev *input_dev = test->priv; + + if (input_dev) + input_unregister_device(input_dev); +} + +static void input_test_poll(struct input_dev *input) { } + +static void input_test_polling(struct kunit *test) +{ + struct input_dev *input_dev = test->priv; + + /* Must fail because a poll handler has not been set-up yet */ + KUNIT_ASSERT_EQ(test, input_get_poll_interval(input_dev), -EINVAL); + + KUNIT_ASSERT_EQ(test, input_setup_polling(input_dev, input_test_poll), 0); + + input_set_poll_interval(input_dev, POLL_INTERVAL); + + /* Must succeed because poll handler was set-up and poll interval set */ + KUNIT_ASSERT_EQ(test, input_get_poll_interval(input_dev), POLL_INTERVAL); +} + +static void input_test_timestamp(struct kunit *test) +{ + const ktime_t invalid_timestamp = ktime_set(0, 0); + struct input_dev *input_dev = test->priv; + ktime_t *timestamp, time; + + timestamp = input_get_timestamp(input_dev); + time = timestamp[INPUT_CLK_MONO]; + + /* The returned timestamp must always be valid */ + KUNIT_ASSERT_EQ(test, ktime_compare(time, invalid_timestamp), 1); + + time = ktime_get(); + input_set_timestamp(input_dev, time); + + timestamp = input_get_timestamp(input_dev); + /* The timestamp must be the same than set before */ + KUNIT_ASSERT_EQ(test, ktime_compare(timestamp[INPUT_CLK_MONO], time), 0); +} + +static void input_test_match_device_id(struct kunit *test) +{ + struct input_dev *input_dev = test->priv; + struct input_device_id id = { 0 }; + + /* + * Must match when the input device bus, vendor, product, version + * and events capable of handling are the same and fail to match + * otherwise. + */ + id.flags = INPUT_DEVICE_ID_MATCH_BUS; + id.bustype = BUS_VIRTUAL; + KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id)); + + id.bustype = BUS_I2C; + KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id)); + + id.flags = INPUT_DEVICE_ID_MATCH_VENDOR; + id.vendor = 1; + KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id)); + + id.vendor = 2; + KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id)); + + id.flags = INPUT_DEVICE_ID_MATCH_PRODUCT; + id.product = 1; + KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id)); + + id.product = 2; + KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id)); + + id.flags = INPUT_DEVICE_ID_MATCH_VERSION; + id.version = 1; + KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id)); + + id.version = 2; + KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id)); + + id.flags = INPUT_DEVICE_ID_MATCH_EVBIT; + __set_bit(EV_KEY, id.evbit); + KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id)); + + __set_bit(EV_ABS, id.evbit); + KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id)); +} + +static void input_test_grab(struct kunit *test) +{ + struct input_dev *input_dev = test->priv; + struct input_handle test_handle; + struct input_handler handler; + struct input_handle handle; + struct input_device_id id; + int res; + + handler.name = "handler"; + handler.id_table = &id; + + handle.dev = input_get_device(input_dev); + handle.name = dev_name(&input_dev->dev); + handle.handler = &handler; + res = input_grab_device(&handle); + KUNIT_ASSERT_TRUE(test, res == 0); + + test_handle.dev = input_get_device(input_dev); + test_handle.name = dev_name(&input_dev->dev); + test_handle.handler = &handler; + res = input_grab_device(&test_handle); + KUNIT_ASSERT_EQ(test, res, -EBUSY); + + input_release_device(&handle); + input_put_device(input_dev); + res = input_grab_device(&test_handle); + KUNIT_ASSERT_TRUE(test, res == 0); + input_put_device(input_dev); +} + +static struct kunit_case input_tests[] = { + KUNIT_CASE(input_test_polling), + KUNIT_CASE(input_test_timestamp), + KUNIT_CASE(input_test_match_device_id), + KUNIT_CASE(input_test_grab), + { /* sentinel */ } +}; + +static struct kunit_suite input_test_suite = { + .name = "input_core", + .init = input_test_init, + .exit = input_test_exit, + .test_cases = input_tests, +}; + +kunit_test_suite(input_test_suite); + +MODULE_AUTHOR("Javier Martinez Canillas "); +MODULE_DESCRIPTION("KUnit test for the input core"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1