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, 54 insertions, 0 deletions

diff --git a/Documentation/doc-guide/checktransupdate.rst b/Documentation/doc-guide/checktransupdate.rst
new file mode 100644
index 000000000..7b25375cc
--- /dev/null
+++ b/Documentation/doc-guide/checktransupdate.rst
@@ -0,0 +1,54 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Checking for needed translation updates
+=======================================
+
+This script helps track the translation status of the documentation in
+different locales, i.e., whether the documentation is up-to-date with
+the English counterpart.
+
+How it works
+------------
+
+It uses ``git log`` command to track the latest English commit from the
+translation commit (order by author date) and the latest English commits
+from HEAD. If any differences occur, the file is considered as out-of-date,
+then commits that need to be updated will be collected and reported.
+
+Features implemented
+
+-  check all files in a certain locale
+-  check a single file or a set of files
+-  provide options to change output format
+-  track the translation status of files that have no translation
+
+Usage
+-----
+
+::
+
+   tools/docs/checktransupdate.py --help
+
+Please refer to the output of argument parser for usage details.
+
+Samples
+
+-  ``tools/docs/checktransupdate.py -l zh_CN``
+   This will print all the files that need to be updated in the zh_CN locale.
+-  ``tools/docs/checktransupdate.py Documentation/translations/zh_CN/dev-tools/testing-overview.rst``
+   This will only print the status of the specified file.
+
+Then the output is something like:
+
+::
+
+    Documentation/dev-tools/kfence.rst
+    No translation in the locale of zh_CN
+
+    Documentation/translations/zh_CN/dev-tools/testing-overview.rst
+    commit 42fb9cfd5b18 ("Documentation: dev-tools: Add link to RV docs")
+    1 commits needs resolving in total
+
+Features to be implemented
+
+- files can be a folder instead of only a file