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, 75 insertions, 0 deletions

diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
new file mode 100644
index 000000000..6d17dfa25
--- /dev/null
+++ b/drivers/mux/Kconfig
@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Multiplexer devices
+#
+
+config MULTIPLEXER
+	bool
+
+config MUX_CORE
+	bool "Generic Multiplexer Support"
+	select MULTIPLEXER
+	help
+	  This framework is designed to abstract multiplexer handling for
+	  devices via various GPIO-, MMIO/Regmap or specific multiplexer
+	  controller chips.
+
+	  If unsure, say no.
+
+if MULTIPLEXER
+
+menu "Multiplexer drivers"
+
+config MUX_ADG792A
+	tristate "Analog Devices ADG792A/ADG792G Multiplexers"
+	depends on I2C
+	help
+	  ADG792A and ADG792G Wide Bandwidth Triple 4:1 Multiplexers
+
+	  The driver supports both operating the three multiplexers in
+	  parallel and operating them independently.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-adg792a.
+
+config MUX_ADGS1408
+	tristate "Analog Devices ADGS1408/ADGS1409 Multiplexers"
+	depends on SPI
+	help
+	  ADGS1408 8:1 multiplexer and ADGS1409 double 4:1 multiplexer
+	  switches.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-adgs1408.
+
+config MUX_GPIO
+	tristate "GPIO-controlled Multiplexer"
+	depends on GPIOLIB || COMPILE_TEST
+	help
+	  GPIO-controlled Multiplexer controller.
+
+	  The driver builds a single multiplexer controller using a number
+	  of gpio pins. For N pins, there will be 2^N possible multiplexer
+	  states. The GPIO pins can be connected (by the hardware) to several
+	  multiplexers, which in that case will be operated in parallel.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-gpio.
+
+config MUX_MMIO
+	tristate "MMIO/Regmap register bitfield-controlled Multiplexer"
+	depends on OF
+	select REGMAP_MMIO
+	help
+	  MMIO/Regmap register bitfield-controlled Multiplexer controller.
+
+	  The driver builds multiplexer controllers for bitfields in either
+	  a syscon register or a driver regmap register. For N bit wide
+	  bitfields, there will be 2^N possible multiplexer states.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-mmio.
+
+endmenu
+
+endif # MULTIPLEXER