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, 94 insertions, 0 deletions

diff --git a/Documentation/input/devices/appletouch.rst b/Documentation/input/devices/appletouch.rst
new file mode 100644
index 000000000..c94470e66
--- /dev/null
+++ b/Documentation/input/devices/appletouch.rst
@@ -0,0 +1,94 @@
+.. include:: <isonum.txt>
+
+----------------------------------
+Apple Touchpad Driver (appletouch)
+----------------------------------
+
+:Copyright: |copy| 2005 Stelian Pop <stelian@popies.net>
+
+appletouch is a Linux kernel driver for the USB touchpad found on post
+February 2005 and October 2005 Apple Aluminium Powerbooks.
+
+This driver is derived from Johannes Berg's appletrackpad driver [#f1]_,
+but it has been improved in some areas:
+
+	* appletouch is a full kernel driver, no userspace program is necessary
+	* appletouch can be interfaced with the synaptics X11 driver, in order
+	  to have touchpad acceleration, scrolling, etc.
+
+Credits go to Johannes Berg for reverse-engineering the touchpad protocol,
+Frank Arnold for further improvements, and Alex Harper for some additional
+information about the inner workings of the touchpad sensors. Michael
+Hanselmann added support for the October 2005 models.
+
+Usage
+-----
+
+In order to use the touchpad in the basic mode, compile the driver and load
+the module. A new input device will be detected and you will be able to read
+the mouse data from /dev/input/mice (using gpm, or X11).
+
+In X11, you can configure the touchpad to use the synaptics X11 driver, which
+will give additional functionalities, like acceleration, scrolling, 2 finger
+tap for middle button mouse emulation, 3 finger tap for right button mouse
+emulation, etc. In order to do this, make sure you're using a recent version of
+the synaptics driver (tested with 0.14.2, available from [#f2]_), and configure
+a new input device in your X11 configuration file (take a look below for an
+example). For additional configuration, see the synaptics driver documentation::
+
+	Section "InputDevice"
+		Identifier      "Synaptics Touchpad"
+		Driver          "synaptics"
+		Option          "SendCoreEvents"        "true"
+		Option          "Device"                "/dev/input/mice"
+		Option          "Protocol"              "auto-dev"
+		Option		"LeftEdge"		"0"
+		Option		"RightEdge"		"850"
+		Option		"TopEdge"		"0"
+		Option		"BottomEdge"		"645"
+		Option		"MinSpeed"		"0.4"
+		Option		"MaxSpeed"		"1"
+		Option		"AccelFactor"		"0.02"
+		Option		"FingerLow"		"0"
+		Option		"FingerHigh"		"30"
+		Option		"MaxTapMove"		"20"
+		Option		"MaxTapTime"		"100"
+		Option		"HorizScrollDelta"	"0"
+		Option		"VertScrollDelta"	"30"
+		Option		"SHMConfig"		"on"
+	EndSection
+
+	Section "ServerLayout"
+		...
+		InputDevice	"Mouse"
+		InputDevice	"Synaptics Touchpad"
+	...
+	EndSection
+
+Fuzz problems
+-------------
+
+The touchpad sensors are very sensitive to heat, and will generate a lot of
+noise when the temperature changes. This is especially true when you power-on
+the laptop for the first time.
+
+The appletouch driver tries to handle this noise and auto adapt itself, but it
+is not perfect. If finger movements are not recognized anymore, try reloading
+the driver.
+
+You can activate debugging using the 'debug' module parameter. A value of 0
+deactivates any debugging, 1 activates tracing of invalid samples, 2 activates
+full tracing (each sample is being traced)::
+
+	modprobe appletouch debug=1
+
+or::
+
+	echo "1" > /sys/module/appletouch/parameters/debug
+
+
+.. Links:
+
+.. [#f1] http://johannes.sipsolutions.net/PowerBook/touchpad/
+
+.. [#f2] `<http://web.archive.org/web/*/http://web.telia.com/~u89404340/touchpad/index.html>`_