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, 78 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-cros-ec b/Documentation/ABI/testing/debugfs-cros-ec
new file mode 100644
index 000000000..9a040c6f5
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-cros-ec
@@ -0,0 +1,78 @@
+What:		/sys/kernel/debug/<cros-ec-device>/console_log
+Date:		September 2017
+KernelVersion:	4.13
+Description:
+		If the EC supports the CONSOLE_READ command type, this file
+		can be used to grab the EC logs. The kernel polls for the log
+		and keeps its own buffer but userspace should grab this and
+		write it out to some logs.
+
+What:		/sys/kernel/debug/<cros-ec-device>/panicinfo
+Date:		September 2017
+KernelVersion:	4.13
+Description:
+		This file dumps the EC panic information from the previous
+		reboot. This file will only exist if the PANIC_INFO command
+		type is supported by the EC.
+
+What:		/sys/kernel/debug/<cros-ec-device>/pdinfo
+Date:		June 2018
+KernelVersion:	4.17
+Description:
+		This file provides the port role, muxes and power debug
+		information for all the USB PD/type-C ports available. If
+		the are no ports available, this file will be just an empty
+		file.
+
+What:		/sys/kernel/debug/<cros-ec-device>/uptime
+Date:		June 2019
+KernelVersion:	5.3
+Description:
+		A u32 providing the time since EC booted in ms. This is
+		is used for synchronizing the AP host time with the EC
+		log. An error is returned if the command is not supported
+		by the EC or there is a communication problem.
+
+What:		/sys/kernel/debug/<cros-ec-device>/last_resume_result
+Date:		June 2019
+KernelVersion:	5.3
+Description:
+		Some ECs have a feature where they will track transitions to
+		the (Intel) processor's SLP_S0 line, in order to detect cases
+		where a system failed to go into S0ix. When the system resumes,
+		an EC with this feature will return a summary of SLP_S0
+		transitions that occurred. The last_resume_result file returns
+		the most recent response from the AP's resume message to the EC.
+
+		The bottom 31 bits contain a count of the number of SLP_S0
+		transitions that occurred since the suspend message was
+		received. Bit 31 is set if the EC attempted to wake the
+		system due to a timeout when watching for SLP_S0 transitions.
+		Callers can use this to detect a wake from the EC due to
+		S0ix timeouts. The result will be zero if no suspend
+		transitions have been attempted, or the EC does not support
+		this feature.
+
+		Output will be in the format: "0x%08x\n".
+
+What:		/sys/kernel/debug/<cros-ec-device>/suspend_timeout_ms
+Date:		August 2022
+KernelVersion:	6.1
+Description:
+		Some ECs have a feature where they will track transitions of
+		a hardware-controlled sleep line, such as Intel's SLP_S0 line,
+		in order to detect cases where a system failed to go into deep
+		sleep states. The suspend_timeout_ms file controls the amount of
+		time in milliseconds the EC will wait before declaring a sleep
+		timeout event and attempting to wake the system.
+
+		Supply 0 to use the default value coded into EC firmware. Supply
+		65535 (EC_HOST_SLEEP_TIMEOUT_INFINITE) to disable the EC sleep
+		failure detection mechanism. Values in between 0 and 65535
+		indicate the number of milliseconds the EC should wait after a
+		sleep transition before declaring a timeout. This includes both
+		the duration after a sleep command was received but before the
+		hardware line changed, as well as the duration between when the
+		hardware line changed and the kernel sent an EC resume command.
+
+		Output will be in the format: "%u\n".