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, 46 insertions, 0 deletions

diff --git a/drivers/accessibility/speakup/DefaultKeyAssignments b/drivers/accessibility/speakup/DefaultKeyAssignments
new file mode 100644
index 000000000..101c803b2
--- /dev/null
+++ b/drivers/accessibility/speakup/DefaultKeyAssignments
@@ -0,0 +1,46 @@
+This file is intended to give you an overview of the default keys used
+by speakup for it's review functions.  You may change them to be
+anything you want but that will take some familiarity with key
+mapping.
+
+We have remapped the insert or zero key on the keypad to act as a
+shift key.  Well, actually as an altgr key.  So in the following list
+InsKeyPad-period means hold down the insert key like a shift key and
+hit the keypad period.
+
+KeyPad-8		Say current Line
+InsKeyPad-8		say from top of screen to reading cursor.
+KeyPad-7		Say Previous Line (UP one line)
+KeyPad-9		Say Next Line (down one line)
+KeyPad-5		Say Current Word
+InsKeyPad-5		Spell Current Word
+KeyPad-4		Say Previous Word (left one word)
+InsKeyPad-4		say from left edge of line to reading cursor.
+KeyPad-6		Say Next Word (right one word)
+InsKeyPad-6		Say from reading cursor to right edge of line.
+KeyPad-2		Say Current Letter
+InsKeyPad-2		say current letter phonetically
+KeyPad-1		Say Previous Character (left one letter)
+KeyPad-3		Say Next Character (right one letter)
+KeyPad-plus		Say Entire Screen
+InsKeyPad-plus		Say from reading cursor line to bottom of screen.
+KeyPad-Minus		Park reading cursor (toggle)
+InsKeyPad-minus		Say character hex and decimal value.
+KeyPad-period		Say Position (current line, position and console)
+InsKeyPad-period	say colour attributes of current position.
+InsKeyPad-9		Move reading cursor to top of screen (insert pgup)
+InsKeyPad-3		Move reading cursor to bottom of screen (insert pgdn)
+InsKeyPad-7		Move reading cursor to left edge of screen (insert home)
+InsKeyPad-1		Move reading cursor to right edge of screen (insert end)
+ControlKeyPad-1		Move reading cursor to last character on current line.
+KeyPad-Enter		Shut Up (until another key is hit) and sync reading cursor
+InsKeyPad-Enter		Shut Up (until toggled back on).
+InsKeyPad-star n<x|y>	go to line (y) or column (x). Where 'n' is any
+		allowed value for the row or column for your current screen.
+KeyPad-/		Mark and Cut screen region.
+InsKeyPad-/		Paste screen region into any console.
+
+Hitting any key while speakup is outputting speech will quiet the
+synth until it has caught up with what is being printed on the
+console.
+