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, 60 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-irq b/Documentation/ABI/testing/sysfs-kernel-irq
new file mode 100644
index 000000000..8910d0c4b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-irq
@@ -0,0 +1,60 @@
+What:		/sys/kernel/irq
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	Directory containing information about the system's IRQs.
+		Specifically, data from the associated struct irq_desc.
+		The information here is similar to that in /proc/interrupts
+		but in a more machine-friendly format.  This directory contains
+		one subdirectory for each Linux IRQ number.
+
+What:		/sys/kernel/irq/<irq>/actions
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	The IRQ action chain.  A comma-separated list of zero or more
+		device names associated with this interrupt.
+
+What:		/sys/kernel/irq/<irq>/chip_name
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	Human-readable chip name supplied by the associated device
+		driver.
+
+What:		/sys/kernel/irq/<irq>/hwirq
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	When interrupt translation domains are used, this file contains
+		the underlying hardware IRQ number used for this Linux IRQ.
+
+What:		/sys/kernel/irq/<irq>/name
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	Human-readable flow handler name as defined by the irq chip
+		driver.
+
+What:		/sys/kernel/irq/<irq>/per_cpu_count
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	The number of times the interrupt has fired since boot.  This
+		is a comma-separated list of counters; one per CPU in CPU id
+		order.  NOTE: This file consistently shows counters for all
+		CPU ids.  This differs from the behavior of /proc/interrupts
+		which only shows counters for online CPUs.
+
+What:		/sys/kernel/irq/<irq>/type
+Date:		September 2016
+KernelVersion:	4.9
+Contact:	Craig Gallek <kraig@google.com>
+Description:	The type of the interrupt.  Either the string 'level' or 'edge'.
+
+What:		/sys/kernel/irq/<irq>/wakeup
+Date:		March 2018
+KernelVersion:	4.17
+Contact:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+Description:	The wakeup state of the interrupt. Either the string
+		'enabled' or 'disabled'.