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, 81 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/dib3000mc.h b/drivers/media/dvb-frontends/dib3000mc.h
new file mode 100644
index 000000000..5ed3d9147
--- /dev/null
+++ b/drivers/media/dvb-frontends/dib3000mc.h
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Driver for DiBcom DiB3000MC/P-demodulator.
+ *
+ * Copyright (C) 2004-6 DiBcom (http://www.dibcom.fr/)
+ * Copyright (C) 2004-5 Patrick Boettcher (patrick.boettcher@posteo.de)
+ *
+ * This code is partially based on the previous dib3000mc.c .
+ */
+#ifndef DIB3000MC_H
+#define DIB3000MC_H
+
+#include "dibx000_common.h"
+
+struct dib3000mc_config {
+	struct dibx000_agc_config *agc;
+
+	u8 phase_noise_mode;
+	u8 impulse_noise_mode;
+
+	u8  pwm3_inversion;
+	u8  use_pwm3;
+	u16 pwm3_value;
+
+	u16 max_time;
+	u16 ln_adc_level;
+
+	u8 agc_command1 :1;
+	u8 agc_command2 :1;
+
+	u8 mobile_mode;
+
+	u8 output_mpeg2_in_188_bytes;
+};
+
+#define DEFAULT_DIB3000MC_I2C_ADDRESS 16
+#define DEFAULT_DIB3000P_I2C_ADDRESS  24
+
+#if IS_REACHABLE(CONFIG_DVB_DIB3000MC)
+extern struct dvb_frontend *dib3000mc_attach(struct i2c_adapter *i2c_adap,
+					     u8 i2c_addr,
+					     struct dib3000mc_config *cfg);
+extern int dib3000mc_i2c_enumeration(struct i2c_adapter *i2c,
+				     int no_of_demods, u8 default_addr,
+				     struct dib3000mc_config cfg[]);
+extern
+struct i2c_adapter *dib3000mc_get_tuner_i2c_master(struct dvb_frontend *demod,
+						   int gating);
+#else
+static inline
+struct dvb_frontend *dib3000mc_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr,
+				      struct dib3000mc_config *cfg)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+
+static inline
+int dib3000mc_i2c_enumeration(struct i2c_adapter *i2c,
+			      int no_of_demods, u8 default_addr,
+			      struct dib3000mc_config cfg[])
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return -ENODEV;
+}
+
+static inline
+struct i2c_adapter *dib3000mc_get_tuner_i2c_master(struct dvb_frontend *demod,
+						   int gating)
+{
+	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
+	return NULL;
+}
+#endif // CONFIG_DVB_DIB3000MC
+
+extern int dib3000mc_pid_control(struct dvb_frontend *fe, int index, int pid,int onoff);
+extern int dib3000mc_pid_parse(struct dvb_frontend *fe, int onoff);
+
+extern void dib3000mc_set_config(struct dvb_frontend *, struct dib3000mc_config *);
+
+#endif