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, 101 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-extcon b/Documentation/ABI/testing/sysfs-class-extcon
new file mode 100644
index 000000000..f8e705375
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-extcon
@@ -0,0 +1,101 @@
+What:		/sys/class/extcon/.../
+Date:		February 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		Provide a place in sysfs for the extcon objects.
+		This allows accessing extcon specific variables.
+		The name of extcon object denoted as ... is the name given
+		with extcon_dev_register.
+
+		One extcon device denotes a single external connector
+		port. An external connector may have multiple cables
+		attached simultaneously. Many of docks, cradles, and
+		accessory cables have such capability. For example,
+		the 30-pin port of Nuri board (/arch/arm/mach-exynos)
+		may have both HDMI and Charger attached, or analog audio,
+		video, and USB cables attached simultaneously.
+
+		If there are cables mutually exclusive with each other,
+		such binary relations may be expressed with extcon_dev's
+		mutually_exclusive array.
+
+What:		/sys/class/extcon/.../name
+Date:		February 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		The /sys/class/extcon/.../name shows the name of the extcon
+		object. If the extcon object has an optional callback
+		"show_name" defined, the callback will provide the name with
+		this sysfs node.
+
+What:		/sys/class/extcon/.../state
+Date:		February 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		The /sys/class/extcon/.../state shows and stores the cable
+		attach/detach information of the corresponding extcon object.
+		If the extcon object has an optional callback "show_state"
+		defined, the showing function is overridden with the optional
+		callback.
+
+		If the default callback for showing function is used, the
+		format is like this::
+
+		    # cat state
+		    USB_OTG=1
+		    HDMI=0
+		    TA=1
+		    EAR_JACK=0
+		    #
+
+		In this example, the extcon device has USB_OTG and TA
+		cables attached and HDMI and EAR_JACK cables detached.
+
+		In order to update the state of an extcon device, enter a hex
+		state number starting with 0x::
+
+		    # echo 0xHEX > state
+
+		This updates the whole state of the extcon device.
+		Inputs of all the methods are required to meet the
+		mutually_exclusive conditions if they exist.
+
+		It is recommended to use this "global" state interface if
+		you need to set the value atomically. The later state
+		interface associated with each cable cannot update
+		multiple cable states of an extcon device simultaneously.
+
+What:		/sys/class/extcon/.../cable.X/name
+Date:		February 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		The /sys/class/extcon/.../cable.X/name shows the name of cable
+		"X" (integer between 0 and 31) of an extcon device.
+
+What:		/sys/class/extcon/.../cable.X/state
+Date:		February 2012
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		The /sys/class/extcon/.../cable.X/state shows and stores the
+		state of cable "X" (integer between 0 and 31) of an extcon
+		device. The state value is either 0 (detached) or 1
+		(attached).
+
+What:		/sys/class/extcon/.../mutually_exclusive/...
+Date:		December 2011
+Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
+Description:
+		Shows the relations of mutually exclusiveness. For example,
+		if the mutually_exclusive array of extcon device is
+		{0x3, 0x5, 0xC, 0x0}, then the output is::
+
+		    # ls mutually_exclusive/
+		    0x3
+		    0x5
+		    0xc
+		    #
+
+		Note that mutually_exclusive is a sub-directory of the extcon
+		device and the file names under the mutually_exclusive
+		directory show the mutually-exclusive sets, not the contents
+		of the files.