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, 48 insertions, 0 deletions

diff --git a/drivers/cpufreq/speedstep-lib.h b/drivers/cpufreq/speedstep-lib.h
new file mode 100644
index 000000000..48329647d
--- /dev/null
+++ b/drivers/cpufreq/speedstep-lib.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * (C) 2002 - 2003 Dominik Brodowski <linux@brodo.de>
+ *
+ *  Library for common functions for Intel SpeedStep v.1 and v.2 support
+ *
+ *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
+ */
+
+
+
+/* processors */
+enum speedstep_processor {
+	SPEEDSTEP_CPU_PIII_C_EARLY = 0x00000001,  /* Coppermine core */
+	SPEEDSTEP_CPU_PIII_C	   = 0x00000002,  /* Coppermine core */
+	SPEEDSTEP_CPU_PIII_T	   = 0x00000003,  /* Tualatin core */
+	SPEEDSTEP_CPU_P4M	   = 0x00000004,  /* P4-M  */
+/* the following processors are not speedstep-capable and are not auto-detected
+ * in speedstep_detect_processor(). However, their speed can be detected using
+ * the speedstep_get_frequency() call. */
+	SPEEDSTEP_CPU_PM	   = 0xFFFFFF03,  /* Pentium M  */
+	SPEEDSTEP_CPU_P4D	   = 0xFFFFFF04,  /* desktop P4  */
+	SPEEDSTEP_CPU_PCORE	   = 0xFFFFFF05,  /* Core */
+};
+
+/* speedstep states -- only two of them */
+
+#define SPEEDSTEP_HIGH	0x00000000
+#define SPEEDSTEP_LOW	0x00000001
+
+
+/* detect a speedstep-capable processor */
+extern enum speedstep_processor speedstep_detect_processor(void);
+
+/* detect the current speed (in khz) of the processor */
+extern unsigned int speedstep_get_frequency(enum speedstep_processor processor);
+
+
+/* detect the low and high speeds of the processor. The callback
+ * set_state"'s first argument is either SPEEDSTEP_HIGH or
+ * SPEEDSTEP_LOW; the second argument is zero so that no
+ * cpufreq_notify_transition calls are initiated.
+ */
+extern int speedstep_get_freqs(enum speedstep_processor processor,
+			       unsigned int *low_speed,
+			       unsigned int *high_speed,
+			       unsigned int *transition_latency,
+			       void (*set_state)(unsigned int state));