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, 173 insertions, 0 deletions

diff --git a/Documentation/sphinx/kernel_abi.py b/Documentation/sphinx/kernel_abi.py
new file mode 100644
index 000000000..5667f207d
--- /dev/null
+++ b/Documentation/sphinx/kernel_abi.py
@@ -0,0 +1,173 @@
+# -*- coding: utf-8; mode: python -*-
+# coding=utf-8
+# SPDX-License-Identifier: GPL-2.0
+#
+"""
+    kernel-abi
+    ~~~~~~~~~~
+
+    Implementation of the ``kernel-abi`` reST-directive.
+
+    :copyright:  Copyright (C) 2016  Markus Heiser
+    :copyright:  Copyright (C) 2016-2020  Mauro Carvalho Chehab
+    :maintained-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
+    :license:    GPL Version 2, June 1991 see Linux/COPYING for details.
+
+    The ``kernel-abi`` (:py:class:`KernelCmd`) directive calls the
+    AbiParser class to parse the Kernel ABI files.
+
+    Overview of directive's argument and options.
+
+    .. code-block:: rst
+
+        .. kernel-abi:: <ABI directory location>
+            :debug:
+
+    The argument ``<ABI directory location>`` is required. It contains the
+    location of the ABI files to be parsed.
+
+    ``debug``
+      Inserts a code-block with the *raw* reST. Sometimes it is helpful to see
+      what reST is generated.
+
+"""
+
+import os
+import re
+import sys
+
+from docutils import nodes, statemachine
+from docutils.statemachine import ViewList
+from docutils.parsers.rst import directives, Directive
+from sphinx.util.docutils import switch_source_input
+from sphinx.util import logging
+
+srctree = os.path.abspath(os.environ["srctree"])
+sys.path.insert(0, os.path.join(srctree, "tools/lib/python"))
+
+from abi.abi_parser import AbiParser
+
+__version__ = "1.0"
+
+logger = logging.getLogger('kernel_abi')
+path = os.path.join(srctree, "Documentation/ABI")
+
+_kernel_abi = None
+
+def get_kernel_abi():
+    """
+    Initialize kernel_abi global var, if not initialized yet.
+
+    This is needed to avoid warnings during Sphinx module initialization.
+    """
+    global _kernel_abi
+
+    if not _kernel_abi:
+        # Parse ABI symbols only once
+        _kernel_abi = AbiParser(path, logger=logger)
+        _kernel_abi.parse_abi()
+        _kernel_abi.check_issues()
+
+    return _kernel_abi
+
+def setup(app):
+
+    app.add_directive("kernel-abi", KernelCmd)
+    return {
+        "version": __version__,
+        "parallel_read_safe": True,
+        "parallel_write_safe": True
+    }
+
+
+class KernelCmd(Directive):
+    """KernelABI (``kernel-abi``) directive"""
+
+    required_arguments = 1
+    optional_arguments = 3
+    has_content = False
+    final_argument_whitespace = True
+    parser = None
+
+    option_spec = {
+        "debug": directives.flag,
+        "no-symbols": directives.flag,
+        "no-files":  directives.flag,
+    }
+
+    def run(self):
+        kernel_abi = get_kernel_abi()
+
+        doc = self.state.document
+        if not doc.settings.file_insertion_enabled:
+            raise self.warning("docutils: file insertion disabled")
+
+        env = self.state.document.settings.env
+        content = ViewList()
+        node = nodes.section()
+
+        abi_type = self.arguments[0]
+
+        if "no-symbols" in self.options:
+            show_symbols = False
+        else:
+            show_symbols = True
+
+        if "no-files" in self.options:
+            show_file = False
+        else:
+            show_file = True
+
+        tab_width = self.options.get('tab-width',
+                                     self.state.document.settings.tab_width)
+
+        old_f = None
+        n = 0
+        n_sym = 0
+        for msg, f, ln in kernel_abi.doc(show_file=show_file,
+                                            show_symbols=show_symbols,
+                                            filter_path=abi_type):
+            n_sym += 1
+            msg_list = statemachine.string2lines(msg, tab_width,
+                                                 convert_whitespace=True)
+            if "debug" in self.options:
+                lines = [
+                    "", "",  ".. code-block:: rst",
+                    "    :linenos:", ""
+                ]
+                for m in msg_list:
+                    lines.append("    " + m)
+            else:
+                lines = msg_list
+
+            for line in lines:
+                # sphinx counts lines from 0
+                content.append(line, f, ln - 1)
+                n += 1
+
+            if f != old_f:
+                # Add the file to Sphinx build dependencies if the file exists
+                fname = os.path.join(srctree, f)
+                if os.path.isfile(fname):
+                    env.note_dependency(fname)
+
+                old_f = f
+
+            # Sphinx doesn't like to parse big messages. So, let's
+            # add content symbol by symbol
+            if content:
+                self.do_parse(content, node)
+                content = ViewList()
+
+        if show_symbols and not show_file:
+            logger.verbose("%s ABI: %i symbols (%i ReST lines)" % (abi_type, n_sym, n))
+        elif not show_symbols and show_file:
+            logger.verbose("%s ABI: %i files (%i ReST lines)" % (abi_type, n_sym, n))
+        else:
+            logger.verbose("%s ABI: %i data (%i ReST lines)" % (abi_type, n_sym, n))
+
+        return node.children
+
+    def do_parse(self, content, node):
+        with switch_source_input(self.state, content):
+            self.state.nested_parse(content, 0, node, match_titles=1)