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, 152 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-powercap b/Documentation/ABI/testing/sysfs-class-powercap
new file mode 100644
index 000000000..ca491ec4e
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-powercap
@@ -0,0 +1,152 @@
+What:		/sys/class/powercap/
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		The powercap/ class sub directory belongs to the power cap
+		subsystem. Refer to
+		Documentation/power/powercap/powercap.rst for details.
+
+What:		/sys/class/powercap/<control type>
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		A <control type> is a unique name under /sys/class/powercap.
+		Here <control type> determines how the power is going to be
+		controlled. A <control type> can contain multiple power zones.
+
+What:		/sys/class/powercap/<control type>/enabled
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		This allows to enable/disable power capping for a "control type".
+		This status affects every power zone using this "control_type.
+
+What:		/sys/class/powercap/<control type>/<power zone>
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		A power zone is a single or a collection of devices, which can
+		be independently monitored and controlled. A power zone sysfs
+		entry is qualified with the name of the <control type>.
+		E.g. intel-rapl:0:1:1.
+
+What:		/sys/class/powercap/<control type>/<power zone>/<child power zone>
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Power zones may be organized in a hierarchy in which child
+		power zones provide monitoring and control for a subset of
+		devices under the parent. For example, if there is a parent
+		power zone for a whole CPU package, each CPU core in it can
+		be a child power zone.
+
+What:		/sys/class/powercap/.../<power zone>/name
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Specifies the name of this power zone.
+
+What:		/sys/class/powercap/.../<power zone>/energy_uj
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Current energy counter in micro-joules. Write "0" to reset.
+		If the counter can not be reset, then this attribute is
+		read-only.
+
+What:		/sys/class/powercap/.../<power zone>/max_energy_range_uj
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Range of the above energy counter in micro-joules.
+
+
+What:		/sys/class/powercap/.../<power zone>/power_uw
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Current power in micro-watts.
+
+What:		/sys/class/powercap/.../<power zone>/max_power_range_uw
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Range of the above power value in micro-watts.
+
+What:		/sys/class/powercap/.../<power zone>/constraint_X_name
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Each power zone can define one or more constraints. Each
+		constraint can have an optional name. Here "X" can have values
+		from 0 to max integer.
+
+What:		/sys/class/powercap/.../<power zone>/constraint_X_power_limit_uw
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Power limit in micro-watts should be applicable for
+		the time window specified by "constraint_X_time_window_us".
+		Here "X" can have values from 0 to max integer.
+
+What:		/sys/class/powercap/.../<power zone>/constraint_X_time_window_us
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Time window in micro seconds. This is used along with
+		constraint_X_power_limit_uw to define a power constraint.
+		Here "X" can have values from 0 to max integer.
+
+
+What:		/sys/class/powercap/<control type>/.../constraint_X_max_power_uw
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Maximum allowed power in micro watts for this constraint.
+		Here "X" can have values from 0 to max integer.
+
+What:		/sys/class/powercap/<control type>/.../constraint_X_min_power_uw
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Minimum allowed power in micro watts for this constraint.
+		Here "X" can have values from 0 to max integer.
+
+What:		/sys/class/powercap/.../<power zone>/constraint_X_max_time_window_us
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Maximum allowed time window in micro seconds for this
+		constraint. Here "X" can have values from 0 to max integer.
+
+What:		/sys/class/powercap/.../<power zone>/constraint_X_min_time_window_us
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		Minimum allowed time window in micro seconds for this
+		constraint. Here "X" can have values from 0 to max integer.
+
+What:		/sys/class/powercap/.../<power zone>/enabled
+Date:		September 2013
+KernelVersion:	3.13
+Contact:	linux-pm@vger.kernel.org
+Description:
+		This allows to enable/disable power capping at power zone level.
+		This applies to current power zone and its children.