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/firewire/device-attribute-test.c | 253 +++++++++++++++++++++++++++++++ 1 file changed, 253 insertions(+) create mode 100644 drivers/firewire/device-attribute-test.c (limited to 'drivers/firewire/device-attribute-test.c') diff --git a/drivers/firewire/device-attribute-test.c b/drivers/firewire/device-attribute-test.c new file mode 100644 index 000000000..97478a96d --- /dev/null +++ b/drivers/firewire/device-attribute-test.c @@ -0,0 +1,253 @@ +// SPDX-License-Identifier: GPL-2.0-only +// +// device-attribute-test.c - An application of Kunit to test implementation for device attributes. +// +// Copyright (c) 2023 Takashi Sakamoto +// +// This file can not be built independently since it is intentionally included in core-device.c. + +#include + +// Configuration ROM for AV/C Devices 1.0 (Dec. 12, 2000, 1394 Trading Association) +// Annex C:Configuration ROM example(informative) +// C.1 Simple AV/C device +// +// Copied from the documentation. +static const u32 simple_avc_config_rom[] = { + 0x0404eabf, + 0x31333934, + 0xe0646102, + 0xffffffff, + 0xffffffff, + 0x00063287, // root directory. + 0x03ffffff, + 0x8100000a, + 0x17ffffff, + 0x8100000e, + 0x0c0083c0, + 0xd1000001, + 0x0004442d, // unit 0 directory. + 0x1200a02d, + 0x13010001, + 0x17ffffff, + 0x81000007, + 0x0005c915, // leaf for textual descriptor. + 0x00000000, + 0x00000000, + 0x56656e64, + 0x6f72204e, + 0x616d6500, + 0x00057f16, // leaf for textual descriptor. + 0x00000000, + 0x00000000, + 0x4d6f6465, + 0x6c204e61, + 0x6d650000, +}; + +// Ibid. +// Annex A:Consideration for configuration ROM reader design (informative) +// A.1 Vendor directory +// +// Written by hand. +static const u32 legacy_avc_config_rom[] = { + 0x04199fe7, + 0x31333934, + 0xe0644000, + 0x00112233, + 0x44556677, + 0x0005dace, // root directory. + 0x03012345, + 0x0c0083c0, + 0x8d000009, + 0xd1000002, + 0xc3000004, + 0x0002e107, // unit 0 directory. + 0x12abcdef, + 0x13543210, + 0x0002cb73, // vendor directory. + 0x17fedcba, + 0x81000004, + 0x00026dc1, // leaf for EUI-64. + 0x00112233, + 0x44556677, + 0x00050e84, // leaf for textual descriptor. + 0x00000000, + 0x00000000, + 0x41424344, + 0x45464748, + 0x494a0000, +}; + +static void device_attr_simple_avc(struct kunit *test) +{ + static const struct fw_device node = { + .device = { + .type = &fw_device_type, + }, + .config_rom = simple_avc_config_rom, + .config_rom_length = sizeof(simple_avc_config_rom), + }; + static const struct fw_unit unit0 = { + .device = { + .type = &fw_unit_type, + .parent = (struct device *)&node.device, + }, + .directory = &simple_avc_config_rom[12], + }; + struct device *node_dev = (struct device *)&node.device; + struct device *unit0_dev = (struct device *)&unit0.device; + static const int unit0_expected_ids[] = {0x00ffffff, 0x00ffffff, 0x0000a02d, 0x00010001}; + char *buf = kunit_kzalloc(test, PAGE_SIZE, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf); + int ids[4] = {0, 0, 0, 0}; + + // Ensure associations for node and unit devices. + + KUNIT_ASSERT_TRUE(test, is_fw_device(node_dev)); + KUNIT_ASSERT_FALSE(test, is_fw_unit(node_dev)); + KUNIT_ASSERT_PTR_EQ(test, fw_device(node_dev), &node); + + KUNIT_ASSERT_FALSE(test, is_fw_device(unit0_dev)); + KUNIT_ASSERT_TRUE(test, is_fw_unit(unit0_dev)); + KUNIT_ASSERT_PTR_EQ(test, fw_parent_device((&unit0)), &node); + KUNIT_ASSERT_PTR_EQ(test, fw_unit(unit0_dev), &unit0); + + // For entries in root directory. + + // Vendor immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[0].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0xffffff\n"); + + // Model immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[4].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0xffffff\n"); + + // Descriptor leaf entry for vendor is found. + KUNIT_EXPECT_GT(test, show_text_leaf(node_dev, &config_rom_attributes[5].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "Vendor Name\n"); + + // Descriptor leaf entry for model is found. + KUNIT_EXPECT_GT(test, show_text_leaf(node_dev, &config_rom_attributes[6].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "Model Name\n"); + + // For entries in unit 0 directory. + + // Vendor immediate entry is not found. + KUNIT_EXPECT_LT(test, show_immediate(unit0_dev, &config_rom_attributes[0].attr, buf), 0); + + // Model immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(unit0_dev, &config_rom_attributes[4].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0xffffff\n"); + + // Descriptor leaf entry for vendor is not found. + KUNIT_EXPECT_LT(test, show_text_leaf(unit0_dev, &config_rom_attributes[5].attr, buf), 0); + + // Descriptor leaf entry for model is found. + KUNIT_EXPECT_GT(test, show_text_leaf(unit0_dev, &config_rom_attributes[6].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "Model Name\n"); + + // Specifier_ID immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(unit0_dev, &config_rom_attributes[2].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0x00a02d\n"); + + // Version immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(unit0_dev, &config_rom_attributes[3].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0x010001\n"); + + kunit_kfree(test, buf); + + get_modalias_ids(&unit0, ids); + KUNIT_EXPECT_MEMEQ(test, ids, unit0_expected_ids, sizeof(ids)); +} + +static void device_attr_legacy_avc(struct kunit *test) +{ + static const struct fw_device node = { + .device = { + .type = &fw_device_type, + }, + .config_rom = legacy_avc_config_rom, + .config_rom_length = sizeof(legacy_avc_config_rom), + }; + static const struct fw_unit unit0 = { + .device = { + .type = &fw_unit_type, + .parent = (struct device *)&node.device, + }, + .directory = &legacy_avc_config_rom[11], + }; + struct device *node_dev = (struct device *)&node.device; + struct device *unit0_dev = (struct device *)&unit0.device; + static const int unit0_expected_ids[] = {0x00012345, 0x00fedcba, 0x00abcdef, 0x00543210}; + char *buf = kunit_kzalloc(test, PAGE_SIZE, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, buf); + int ids[4] = {0, 0, 0, 0}; + + // Ensure associations for node and unit devices. + + KUNIT_ASSERT_TRUE(test, is_fw_device(node_dev)); + KUNIT_ASSERT_FALSE(test, is_fw_unit(node_dev)); + KUNIT_ASSERT_PTR_EQ(test, fw_device((node_dev)), &node); + + KUNIT_ASSERT_FALSE(test, is_fw_device(unit0_dev)); + KUNIT_ASSERT_TRUE(test, is_fw_unit(unit0_dev)); + KUNIT_ASSERT_PTR_EQ(test, fw_parent_device((&unit0)), &node); + KUNIT_ASSERT_PTR_EQ(test, fw_unit(unit0_dev), &unit0); + + // For entries in root directory. + + // Vendor immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[0].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0x012345\n"); + + // Model immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(node_dev, &config_rom_attributes[4].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0xfedcba\n"); + + // Descriptor leaf entry for vendor is not found. + KUNIT_EXPECT_LT(test, show_text_leaf(node_dev, &config_rom_attributes[5].attr, buf), 0); + + // Descriptor leaf entry for model is found. + KUNIT_EXPECT_GT(test, show_text_leaf(node_dev, &config_rom_attributes[6].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "ABCDEFGHIJ\n"); + + // For entries in unit 0 directory. + + // Vendor immediate entry is not found. + KUNIT_EXPECT_LT(test, show_immediate(unit0_dev, &config_rom_attributes[0].attr, buf), 0); + + // Model immediate entry is not found. + KUNIT_EXPECT_LT(test, show_immediate(unit0_dev, &config_rom_attributes[4].attr, buf), 0); + + // Descriptor leaf entry for vendor is not found. + KUNIT_EXPECT_LT(test, show_text_leaf(unit0_dev, &config_rom_attributes[5].attr, buf), 0); + + // Descriptor leaf entry for model is not found. + KUNIT_EXPECT_LT(test, show_text_leaf(unit0_dev, &config_rom_attributes[6].attr, buf), 0); + + // Specifier_ID immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(unit0_dev, &config_rom_attributes[2].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0xabcdef\n"); + + // Version immediate entry is found. + KUNIT_EXPECT_GT(test, show_immediate(unit0_dev, &config_rom_attributes[3].attr, buf), 0); + KUNIT_EXPECT_STREQ(test, buf, "0x543210\n"); + + kunit_kfree(test, buf); + + get_modalias_ids(&unit0, ids); + KUNIT_EXPECT_MEMEQ(test, ids, unit0_expected_ids, sizeof(ids)); +} + +static struct kunit_case device_attr_test_cases[] = { + KUNIT_CASE(device_attr_simple_avc), + KUNIT_CASE(device_attr_legacy_avc), + {} +}; + +static struct kunit_suite device_attr_test_suite = { + .name = "firewire-device-attribute", + .test_cases = device_attr_test_cases, +}; +kunit_test_suite(device_attr_test_suite); -- cgit v1.3.1