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, 45 insertions, 0 deletions

diff --git a/drivers/ptp/ptp_fc3.h b/drivers/ptp/ptp_fc3.h
new file mode 100644
index 000000000..897101579
--- /dev/null
+++ b/drivers/ptp/ptp_fc3.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * PTP hardware clock driver for the FemtoClock3 family of timing and
+ * synchronization devices.
+ *
+ * Copyright (C) 2023 Integrated Device Technology, Inc., a Renesas Company.
+ */
+#ifndef PTP_IDTFC3_H
+#define PTP_IDTFC3_H
+
+#include <linux/ktime.h>
+#include <linux/ptp_clock.h>
+#include <linux/regmap.h>
+
+#define FW_FILENAME	"idtfc3.bin"
+
+#define MAX_FFO_PPB	(244000)
+#define TDC_GET_PERIOD	(10)
+
+struct idtfc3 {
+	struct ptp_clock_info	caps;
+	struct ptp_clock	*ptp_clock;
+	struct device		*dev;
+	/* Mutex to protect operations from being interrupted */
+	struct mutex		*lock;
+	struct device		*mfd;
+	struct regmap		*regmap;
+	struct idtfc3_hw_param	hw_param;
+	u32			sub_sync_count;
+	u32			ns_per_sync;
+	int			tdc_offset_sign;
+	u64			tdc_apll_freq;
+	u32			time_ref_freq;
+	u16			fod_n;
+	u8			lpf_mode;
+	/* Time counter */
+	u32			last_counter;
+	s64			ns;
+	u32			ns_per_counter;
+	u32			tc_update_period;
+	u32			tc_write_timeout;
+	s64			tod_write_overhead;
+};
+
+#endif /* PTP_IDTFC3_H */