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, 241 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/configfs-most b/Documentation/ABI/testing/configfs-most
new file mode 100644
index 000000000..0a4b8649a
--- /dev/null
+++ b/Documentation/ABI/testing/configfs-most
@@ -0,0 +1,241 @@
+What: 		/sys/kernel/config/most_<component>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description: 	Interface is used to configure and connect device channels
+		to component drivers.
+
+		Attributes are visible only when configfs is mounted. To mount
+		configfs in /sys/kernel/config directory use:
+		# mount -t configfs none /sys/kernel/config/
+
+
+What: 		/sys/kernel/config/most_cdev/<link>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description:
+		The attributes:
+
+		buffer_size
+				configure the buffer size for this channel
+
+		subbuffer_size
+				configure the sub-buffer size for this channel
+				(needed for synchronous and isochronous data)
+
+
+		num_buffers
+				configure number of buffers used for this
+				channel
+
+		datatype
+				configure type of data that will travel over
+				this channel
+
+		direction
+				configure whether this link will be an input
+				or output
+
+		dbr_size
+				configure DBR data buffer size (this is used
+				for MediaLB communication only)
+
+		packets_per_xact
+				configure the number of packets that will be
+				collected from the network before being
+				transmitted via USB (this is used for USB
+				communication only)
+
+		device
+				name of the device the link is to be attached to
+
+		channel
+				name of the channel the link is to be attached to
+
+		comp_params
+				pass parameters needed by some components
+
+		create_link
+				write '1' to this attribute to trigger the
+				creation of the link. In case of speculative
+				configuration, the creation is post-poned until
+				a physical device is being attached to the bus.
+
+		destroy_link
+				write '1' to this attribute to destroy an
+				active link
+
+What: 		/sys/kernel/config/most_video/<link>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description:
+		The attributes:
+
+		buffer_size
+				configure the buffer size for this channel
+
+		subbuffer_size
+				configure the sub-buffer size for this channel
+				(needed for synchronous and isochronous data)
+
+
+		num_buffers
+				configure number of buffers used for this
+				channel
+
+		datatype
+				configure type of data that will travel over
+				this channel
+
+		direction
+				configure whether this link will be an input
+				or output
+
+		dbr_size
+				configure DBR data buffer size (this is used
+				for MediaLB communication only)
+
+		packets_per_xact
+				configure the number of packets that will be
+				collected from the network before being
+				transmitted via USB (this is used for USB
+				communication only)
+
+		device
+				name of the device the link is to be attached to
+
+		channel
+				name of the channel the link is to be attached to
+
+		comp_params
+				pass parameters needed by some components
+
+		create_link
+				write '1' to this attribute to trigger the
+				creation of the link. In case of speculative
+				configuration, the creation is post-poned until
+				a physical device is being attached to the bus.
+
+		destroy_link
+				write '1' to this attribute to destroy an
+				active link
+
+What: 		/sys/kernel/config/most_net/<link>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description:
+		The attributes:
+
+		buffer_size
+				configure the buffer size for this channel
+
+		subbuffer_size
+				configure the sub-buffer size for this channel
+				(needed for synchronous and isochronous data)
+
+
+		num_buffers
+				configure number of buffers used for this
+				channel
+
+		datatype
+				configure type of data that will travel over
+				this channel
+
+		direction
+				configure whether this link will be an input
+				or output
+
+		dbr_size
+				configure DBR data buffer size (this is used
+				for MediaLB communication only)
+
+		packets_per_xact
+				configure the number of packets that will be
+				collected from the network before being
+				transmitted via USB (this is used for USB
+				communication only)
+
+		device
+				name of the device the link is to be attached to
+
+		channel
+				name of the channel the link is to be attached to
+
+		comp_params
+				pass parameters needed by some components
+
+		create_link
+				write '1' to this attribute to trigger the
+				creation of the link. In case of speculative
+				configuration, the creation is post-poned until
+				a physical device is being attached to the bus.
+
+		destroy_link
+				write '1' to this attribute to destroy an
+				active link
+
+What: 		/sys/kernel/config/most_sound/<card>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description:
+		The attributes:
+
+		create_card
+				write '1' to this attribute to trigger the
+                                registration of the sound card with the ALSA
+				subsystem.
+
+What: 		/sys/kernel/config/most_sound/<card>/<link>
+Date: 		March 8, 2019
+KernelVersion:  5.2
+Description:
+		The attributes:
+
+		buffer_size
+				configure the buffer size for this channel
+
+		subbuffer_size
+				configure the sub-buffer size for this channel
+				(needed for synchronous and isochronous data)
+
+
+		num_buffers
+				configure number of buffers used for this
+				channel
+
+		datatype
+				configure type of data that will travel over
+				this channel
+
+		direction
+				configure whether this link will be an input
+				or output
+
+		dbr_size
+				configure DBR data buffer size (this is used
+				for MediaLB communication only)
+
+		packets_per_xact
+				configure the number of packets that will be
+				collected from the network before being
+				transmitted via USB (this is used for USB
+				communication only)
+
+		device
+				name of the device the link is to be attached to
+
+		channel
+				name of the channel the link is to be attached to
+
+		comp_params
+				pass parameters needed by some components
+
+		create_link
+				write '1' to this attribute to trigger the
+				creation of the link. In case of speculative
+				configuration, the creation is post-poned until
+				a physical device is being attached to the bus.
+
+		destroy_link
+				write '1' to this attribute to destroy an
+				active link