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, 242 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/stb6000.c b/drivers/media/dvb-frontends/stb6000.c
new file mode 100644
index 000000000..c66d4ac17
--- /dev/null
+++ b/drivers/media/dvb-frontends/stb6000.c
@@ -0,0 +1,242 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+  /*
+     Driver for ST STB6000 DVBS Silicon tuner
+
+     Copyright (C) 2008 Igor M. Liplianin (liplianin@me.by)
+
+
+  */
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/dvb/frontend.h>
+#include <asm/types.h>
+
+#include "stb6000.h"
+
+static int debug;
+#define dprintk(args...) \
+	do { \
+		if (debug) \
+			printk(KERN_DEBUG "stb6000: " args); \
+	} while (0)
+
+struct stb6000_priv {
+	/* i2c details */
+	int i2c_address;
+	struct i2c_adapter *i2c;
+	u32 frequency;
+};
+
+static void stb6000_release(struct dvb_frontend *fe)
+{
+	kfree(fe->tuner_priv);
+	fe->tuner_priv = NULL;
+}
+
+static int stb6000_sleep(struct dvb_frontend *fe)
+{
+	struct stb6000_priv *priv = fe->tuner_priv;
+	int ret;
+	u8 buf[] = { 10, 0 };
+	struct i2c_msg msg = {
+		.addr = priv->i2c_address,
+		.flags = 0,
+		.buf = buf,
+		.len = 2
+	};
+
+	dprintk("%s:\n", __func__);
+
+	if (fe->ops.i2c_gate_ctrl)
+		fe->ops.i2c_gate_ctrl(fe, 1);
+
+	ret = i2c_transfer(priv->i2c, &msg, 1);
+	if (ret != 1)
+		dprintk("%s: i2c error\n", __func__);
+
+	if (fe->ops.i2c_gate_ctrl)
+		fe->ops.i2c_gate_ctrl(fe, 0);
+
+	return (ret == 1) ? 0 : ret;
+}
+
+static int stb6000_set_params(struct dvb_frontend *fe)
+{
+	struct dtv_frontend_properties *p = &fe->dtv_property_cache;
+	struct stb6000_priv *priv = fe->tuner_priv;
+	unsigned int n, m;
+	int ret;
+	u32 freq_mhz;
+	int bandwidth;
+	u8 buf[12];
+	struct i2c_msg msg = {
+		.addr = priv->i2c_address,
+		.flags = 0,
+		.buf = buf,
+		.len = 12
+	};
+
+	dprintk("%s:\n", __func__);
+
+	freq_mhz = p->frequency / 1000;
+	bandwidth = p->symbol_rate / 1000000;
+
+	if (bandwidth > 31)
+		bandwidth = 31;
+
+	if ((freq_mhz > 949) && (freq_mhz < 2151)) {
+		buf[0] = 0x01;
+		buf[1] = 0xac;
+		if (freq_mhz < 1950)
+			buf[1] = 0xaa;
+		if (freq_mhz < 1800)
+			buf[1] = 0xa8;
+		if (freq_mhz < 1650)
+			buf[1] = 0xa6;
+		if (freq_mhz < 1530)
+			buf[1] = 0xa5;
+		if (freq_mhz < 1470)
+			buf[1] = 0xa4;
+		if (freq_mhz < 1370)
+			buf[1] = 0xa2;
+		if (freq_mhz < 1300)
+			buf[1] = 0xa1;
+		if (freq_mhz < 1200)
+			buf[1] = 0xa0;
+		if (freq_mhz < 1075)
+			buf[1] = 0xbc;
+		if (freq_mhz < 1000)
+			buf[1] = 0xba;
+		if (freq_mhz < 1075) {
+			n = freq_mhz / 8; /* vco=lo*4 */
+			m = 2;
+		} else {
+			n = freq_mhz / 16; /* vco=lo*2 */
+			m = 1;
+		}
+		buf[2] = n >> 1;
+		buf[3] = (unsigned char)(((n & 1) << 7) |
+					(m * freq_mhz - n * 16) | 0x60);
+		buf[4] = 0x04;
+		buf[5] = 0x0e;
+
+		buf[6] = (unsigned char)(bandwidth);
+
+		buf[7] = 0xd8;
+		buf[8] = 0xd0;
+		buf[9] = 0x50;
+		buf[10] = 0xeb;
+		buf[11] = 0x4f;
+
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 1);
+
+		ret = i2c_transfer(priv->i2c, &msg, 1);
+		if (ret != 1)
+			dprintk("%s: i2c error\n", __func__);
+
+		udelay(10);
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 0);
+
+		buf[0] = 0x07;
+		buf[1] = 0xdf;
+		buf[2] = 0xd0;
+		buf[3] = 0x50;
+		buf[4] = 0xfb;
+		msg.len = 5;
+
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 1);
+
+		ret = i2c_transfer(priv->i2c, &msg, 1);
+		if (ret != 1)
+			dprintk("%s: i2c error\n", __func__);
+
+		udelay(10);
+		if (fe->ops.i2c_gate_ctrl)
+			fe->ops.i2c_gate_ctrl(fe, 0);
+
+		priv->frequency = freq_mhz * 1000;
+
+		return (ret == 1) ? 0 : ret;
+	}
+	return -1;
+}
+
+static int stb6000_get_frequency(struct dvb_frontend *fe, u32 *frequency)
+{
+	struct stb6000_priv *priv = fe->tuner_priv;
+	*frequency = priv->frequency;
+	return 0;
+}
+
+static const struct dvb_tuner_ops stb6000_tuner_ops = {
+	.info = {
+		.name = "ST STB6000",
+		.frequency_min_hz =  950 * MHz,
+		.frequency_max_hz = 2150 * MHz
+	},
+	.release = stb6000_release,
+	.sleep = stb6000_sleep,
+	.set_params = stb6000_set_params,
+	.get_frequency = stb6000_get_frequency,
+};
+
+struct dvb_frontend *stb6000_attach(struct dvb_frontend *fe, int addr,
+						struct i2c_adapter *i2c)
+{
+	struct stb6000_priv *priv = NULL;
+	u8 b0[] = { 0 };
+	u8 b1[] = { 0, 0 };
+	struct i2c_msg msg[2] = {
+		{
+			.addr = addr,
+			.flags = 0,
+			.buf = b0,
+			.len = 0
+		}, {
+			.addr = addr,
+			.flags = I2C_M_RD,
+			.buf = b1,
+			.len = 2
+		}
+	};
+	int ret;
+
+	dprintk("%s:\n", __func__);
+
+	if (fe->ops.i2c_gate_ctrl)
+		fe->ops.i2c_gate_ctrl(fe, 1);
+
+	/* is some i2c device here ? */
+	ret = i2c_transfer(i2c, msg, 2);
+	if (fe->ops.i2c_gate_ctrl)
+		fe->ops.i2c_gate_ctrl(fe, 0);
+
+	if (ret != 2)
+		return NULL;
+
+	priv = kzalloc_obj(struct stb6000_priv);
+	if (priv == NULL)
+		return NULL;
+
+	priv->i2c_address = addr;
+	priv->i2c = i2c;
+
+	memcpy(&fe->ops.tuner_ops, &stb6000_tuner_ops,
+				sizeof(struct dvb_tuner_ops));
+
+	fe->tuner_priv = priv;
+
+	return fe;
+}
+EXPORT_SYMBOL_GPL(stb6000_attach);
+
+module_param(debug, int, 0644);
+MODULE_PARM_DESC(debug, "Turn on/off frontend debugging (default:off).");
+
+MODULE_DESCRIPTION("DVB STB6000 driver");
+MODULE_AUTHOR("Igor M. Liplianin <liplianin@me.by>");
+MODULE_LICENSE("GPL");