1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0
#
# Copyright (c) 2025 Intel Corporation
#
# Test for indirect target selection (ITS) mitigation.
#
# Tests if the RETs are correctly patched by evaluating the
# vmlinux .return_sites in /proc/kcore.
#
# Install dependencies
# add-apt-repository ppa:michel-slm/kernel-utils
# apt update
# apt install -y python3-drgn python3-pyelftools python3-capstone
#
# Run on target machine
# mkdir -p /usr/lib/debug/lib/modules/$(uname -r)
# cp $VMLINUX /usr/lib/debug/lib/modules/$(uname -r)/vmlinux
#
# Usage: ./its_ret_alignment.py
import os, sys, argparse
from pathlib import Path
this_dir = os.path.dirname(os.path.realpath(__file__))
sys.path.insert(0, this_dir + '/../../kselftest')
import ksft
import common as c
bug = "indirect_target_selection"
mitigation = c.get_sysfs(bug)
if not mitigation or "Aligned branch/return thunks" not in mitigation:
ksft.test_result_skip("Skipping its_ret_alignment.py: Aligned branch/return thunks not enabled")
ksft.finished()
c.check_dependencies_or_skip(['drgn', 'elftools', 'capstone'], script_name="its_ret_alignment.py")
from elftools.elf.elffile import ELFFile
from drgn.helpers.common.memory import identify_address
cap = c.init_capstone()
if len(os.sys.argv) > 1:
arg_vmlinux = os.sys.argv[1]
if not os.path.exists(arg_vmlinux):
ksft.test_result_fail(f"its_ret_alignment.py: vmlinux not found at user-supplied path: {arg_vmlinux}")
ksft.exit_fail()
os.makedirs(f"/usr/lib/debug/lib/modules/{os.uname().release}", exist_ok=True)
os.system(f'cp {arg_vmlinux} /usr/lib/debug/lib/modules/$(uname -r)/vmlinux')
vmlinux = f"/usr/lib/debug/lib/modules/{os.uname().release}/vmlinux"
if not os.path.exists(vmlinux):
ksft.test_result_fail(f"its_ret_alignment.py: vmlinux not found at {vmlinux}")
ksft.exit_fail()
ksft.print_msg(f"Using vmlinux: {vmlinux}")
rethunks_start_vmlinux, rethunks_sec_offset, size = c.get_section_info(vmlinux, '.return_sites')
ksft.print_msg(f"vmlinux: Section .return_sites (0x{rethunks_start_vmlinux:x}) found at 0x{rethunks_sec_offset:x} with size 0x{size:x}")
sites_offset = c.get_patch_sites(vmlinux, rethunks_sec_offset, size)
total_rethunk_tests = len(sites_offset)
ksft.print_msg(f"Found {total_rethunk_tests} rethunk sites")
prog = c.get_runtime_kernel()
rethunks_start_kcore = prog.symbol('__return_sites').address
ksft.print_msg(f'kcore: __rethunk_sites: 0x{rethunks_start_kcore:x}')
its_return_thunk = prog.symbol('its_return_thunk').address
ksft.print_msg(f'kcore: its_return_thunk: 0x{its_return_thunk:x}')
tests_passed = 0
tests_failed = 0
tests_unknown = 0
tests_skipped = 0
with open(vmlinux, 'rb') as f:
elffile = ELFFile(f)
text_section = elffile.get_section_by_name('.text')
for i in range(len(sites_offset)):
site = rethunks_start_kcore + sites_offset[i]
vmlinux_site = rethunks_start_vmlinux + sites_offset[i]
try:
passed = unknown = failed = skipped = False
symbol = identify_address(prog, site)
vmlinux_insn = c.get_instruction_from_vmlinux(elffile, text_section, text_section['sh_addr'], vmlinux_site)
kcore_insn = list(cap.disasm(prog.read(site, 16), site))[0]
insn_end = site + kcore_insn.size - 1
safe_site = insn_end & 0x20
site_status = "" if safe_site else "(unsafe)"
ksft.print_msg(f"\nSite {i}: {symbol} <0x{site:x}> {site_status}")
ksft.print_msg(f"\tvmlinux: 0x{vmlinux_insn.address:x}:\t{vmlinux_insn.mnemonic}\t{vmlinux_insn.op_str}")
ksft.print_msg(f"\tkcore: 0x{kcore_insn.address:x}:\t{kcore_insn.mnemonic}\t{kcore_insn.op_str}")
if safe_site:
tests_passed += 1
passed = True
ksft.print_msg(f"\tPASSED: At safe address")
continue
if "jmp" in kcore_insn.mnemonic:
passed = True
elif "ret" not in kcore_insn.mnemonic:
skipped = True
if passed:
ksft.print_msg(f"\tPASSED: Found {kcore_insn.mnemonic} {kcore_insn.op_str}")
tests_passed += 1
elif skipped:
ksft.print_msg(f"\tSKIPPED: Found '{kcore_insn.mnemonic}'")
tests_skipped += 1
elif unknown:
ksft.print_msg(f"UNKNOWN: An unknown instruction: {kcore_insn}")
tests_unknown += 1
else:
ksft.print_msg(f'\t************* FAILED *************')
ksft.print_msg(f"\tFound {kcore_insn.mnemonic} {kcore_insn.op_str}")
ksft.print_msg(f'\t**********************************')
tests_failed += 1
except Exception as e:
ksft.print_msg(f"UNKNOWN: An unexpected error occurred: {e}")
tests_unknown += 1
ksft.print_msg(f"\n\nSummary:")
ksft.print_msg(f"PASSED: \t{tests_passed} \t/ {total_rethunk_tests}")
ksft.print_msg(f"FAILED: \t{tests_failed} \t/ {total_rethunk_tests}")
ksft.print_msg(f"SKIPPED: \t{tests_skipped} \t/ {total_rethunk_tests}")
ksft.print_msg(f"UNKNOWN: \t{tests_unknown} \t/ {total_rethunk_tests}")
if tests_failed == 0:
ksft.test_result_pass("All ITS return thunk sites passed.")
else:
ksft.test_result_fail(f"{tests_failed} failed sites need ITS return thunks.")
ksft.finished()
|
