x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 275 insertions, 0 deletions

diff --git a/Documentation/sphinx/kerneldoc.py b/Documentation/sphinx/kerneldoc.py
new file mode 100644
index 000000000..c1cadb4eb
--- /dev/null
+++ b/Documentation/sphinx/kerneldoc.py
@@ -0,0 +1,275 @@
+# coding=utf-8
+# SPDX-License-Identifier: MIT
+#
+# Copyright © 2016 Intel Corporation
+#
+# Permission is hereby granted, free of charge, to any person obtaining a
+# copy of this software and associated documentation files (the "Software"),
+# to deal in the Software without restriction, including without limitation
+# the rights to use, copy, modify, merge, publish, distribute, sublicense,
+# and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice (including the next
+# paragraph) shall be included in all copies or substantial portions of the
+# Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+# THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+# IN THE SOFTWARE.
+#
+# Authors:
+#    Jani Nikula <jani.nikula@intel.com>
+#
+
+import codecs
+import os
+import subprocess
+import sys
+import re
+import glob
+
+from docutils import nodes, statemachine
+from docutils.statemachine import ViewList
+from docutils.parsers.rst import directives, Directive
+import sphinx
+from sphinx.util.docutils import switch_source_input
+from sphinx.util import logging
+from pprint import pformat
+
+srctree = os.path.abspath(os.environ["srctree"])
+sys.path.insert(0, os.path.join(srctree, "tools/lib/python"))
+
+from kdoc.kdoc_files import KernelFiles
+from kdoc.kdoc_output import RestFormat
+
+# Used when verbose is active to show how to reproduce kernel-doc
+# issues via command line
+kerneldoc_bin = "tools/docs/kernel-doc"
+
+__version__  = '1.0'
+kfiles = None
+logger = logging.getLogger(__name__)
+
+def cmd_str(cmd):
+    """
+    Helper function to output a command line that can be used to produce
+    the same records via command line. Helpful to debug troubles at the
+    script.
+    """
+
+    cmd_line = ""
+
+    for w in cmd:
+        if w == "" or " " in w:
+            esc_cmd = "'" + w + "'"
+        else:
+            esc_cmd = w
+
+        if cmd_line:
+            cmd_line += " " + esc_cmd
+            continue
+        else:
+            cmd_line = esc_cmd
+
+    return cmd_line
+
+class KernelDocDirective(Directive):
+    """Extract kernel-doc comments from the specified file"""
+    required_argument = 1
+    optional_arguments = 4
+    option_spec = {
+        'doc': directives.unchanged_required,
+        'export': directives.unchanged,
+        'internal': directives.unchanged,
+        'identifiers': directives.unchanged,
+        'no-identifiers': directives.unchanged,
+        'functions': directives.unchanged,
+    }
+    has_content = False
+    verbose = 0
+
+    parse_args = {}
+    msg_args = {}
+
+    def handle_args(self):
+
+        env = self.state.document.settings.env
+        cmd = [kerneldoc_bin, '-rst', '-enable-lineno']
+
+        filename = env.config.kerneldoc_srctree + '/' + self.arguments[0]
+
+        # Arguments used by KernelFiles.parse() function
+        self.parse_args = {
+            "file_list": [filename],
+            "export_file": []
+        }
+
+        # Arguments used by KernelFiles.msg() function
+        self.msg_args = {
+            "enable_lineno": True,
+            "export": False,
+            "internal": False,
+            "symbol": [],
+            "nosymbol": [],
+            "no_doc_sections": False
+        }
+
+        export_file_patterns = []
+
+        verbose = os.environ.get("V")
+        if verbose:
+            try:
+                self.verbose = int(verbose)
+            except ValueError:
+                pass
+
+        # Tell sphinx of the dependency
+        env.note_dependency(os.path.abspath(filename))
+
+        self.tab_width = self.options.get('tab-width',
+                                          self.state.document.settings.tab_width)
+
+        # 'function' is an alias of 'identifiers'
+        if 'functions' in self.options:
+            self.options['identifiers'] = self.options.get('functions')
+
+        # FIXME: make this nicer and more robust against errors
+        if 'export' in self.options:
+            cmd += ['-export']
+            self.msg_args["export"] = True
+            export_file_patterns = str(self.options.get('export')).split()
+        elif 'internal' in self.options:
+            cmd += ['-internal']
+            self.msg_args["internal"] = True
+            export_file_patterns = str(self.options.get('internal')).split()
+        elif 'doc' in self.options:
+            func = str(self.options.get('doc'))
+            cmd += ['-function', func]
+            self.msg_args["symbol"].append(func)
+        elif 'identifiers' in self.options:
+            identifiers = self.options.get('identifiers').split()
+            if identifiers:
+                for i in identifiers:
+                    i = i.rstrip("\\").strip()
+                    if not i:
+                        continue
+
+                    cmd += ['-function', i]
+                    self.msg_args["symbol"].append(i)
+            else:
+                cmd += ['-no-doc-sections']
+                self.msg_args["no_doc_sections"] = True
+
+        if 'no-identifiers' in self.options:
+            no_identifiers = self.options.get('no-identifiers').split()
+            if no_identifiers:
+                for i in no_identifiers:
+                    i = i.rstrip("\\").strip()
+                    if not i:
+                        continue
+
+                    cmd += ['-nosymbol', i]
+                    self.msg_args["nosymbol"].append(i)
+
+        for pattern in export_file_patterns:
+            pattern = pattern.rstrip("\\").strip()
+            if not pattern:
+                continue
+
+            for f in glob.glob(env.config.kerneldoc_srctree + '/' + pattern):
+                env.note_dependency(os.path.abspath(f))
+                cmd += ['-export-file', f]
+                self.parse_args["export_file"].append(f)
+
+            # Export file is needed by both parse and msg, as kernel-doc
+            # cache exports.
+            self.msg_args["export_file"] = self.parse_args["export_file"]
+
+        cmd += [filename]
+
+        return cmd
+
+    def parse_msg(self, filename, node, out):
+        """
+        Handles a kernel-doc output for a given file
+        """
+
+        env = self.state.document.settings.env
+
+        lines = statemachine.string2lines(out, self.tab_width,
+                                            convert_whitespace=True)
+        result = ViewList()
+
+        lineoffset = 0;
+        line_regex = re.compile(r"^\.\. LINENO ([0-9]+)$")
+        for line in lines:
+            match = line_regex.search(line)
+            if match:
+                # sphinx counts lines from 0
+                lineoffset = int(match.group(1)) - 1
+                # we must eat our comments since the upset the markup
+            else:
+                doc = str(env.srcdir) + "/" + env.docname + ":" + str(self.lineno)
+                result.append(line, doc + ": " + filename, lineoffset)
+                lineoffset += 1
+
+        self.do_parse(result, node)
+
+    def run_kdoc(self, kfiles):
+        """
+        Execute kernel-doc classes directly instead of running as a separate
+        command.
+        """
+
+        env = self.state.document.settings.env
+
+        node = nodes.section()
+
+        kfiles.parse(**self.parse_args)
+        filenames = self.parse_args["file_list"]
+
+        for filename, out in kfiles.msg(**self.msg_args, filenames=filenames):
+            self.parse_msg(filename, node, out)
+
+        return node.children
+
+    def run(self):
+        cmd = self.handle_args()
+        if self.verbose >= 1:
+            logger.info(cmd_str(cmd))
+
+        try:
+            return self.run_kdoc(kfiles)
+        except Exception as e:  # pylint: disable=W0703
+            logger.warning("kernel-doc '%s' processing failed with: %s" %
+                           (cmd_str(cmd), pformat(e)))
+            return [nodes.error(None, nodes.paragraph(text = "kernel-doc missing"))]
+
+    def do_parse(self, result, node):
+        with switch_source_input(self.state, result):
+            self.state.nested_parse(result, 0, node, match_titles=1)
+
+def setup_kfiles(app):
+    global kfiles
+    out_style = RestFormat()
+    kfiles = KernelFiles(out_style=out_style, logger=logger)
+
+
+def setup(app):
+    app.add_config_value('kerneldoc_srctree', None, 'env')
+    app.add_config_value('kerneldoc_verbosity', 1, 'env')
+
+    app.add_directive('kernel-doc', KernelDocDirective)
+
+    app.connect('builder-inited', setup_kfiles)
+
+    return dict(
+        version = __version__,
+        parallel_read_safe = True,
+        parallel_write_safe = True
+    )