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, 396 insertions, 0 deletions

diff --git a/drivers/media/dvb-frontends/itd1000.c b/drivers/media/dvb-frontends/itd1000.c
new file mode 100644
index 000000000..f5f023639
--- /dev/null
+++ b/drivers/media/dvb-frontends/itd1000.c
@@ -0,0 +1,396 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Driver for the Integrant ITD1000 "Zero-IF Tuner IC for Direct Broadcast Satellite"
+ *
+ *  Copyright (c) 2007-8 Patrick Boettcher <pb@linuxtv.org>
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/delay.h>
+#include <linux/dvb/frontend.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+
+#include <media/dvb_frontend.h>
+
+#include "itd1000.h"
+#include "itd1000_priv.h"
+
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  64
+
+static int debug;
+module_param(debug, int, 0644);
+MODULE_PARM_DESC(debug, "Turn on/off debugging (default:off).");
+
+#define itd_dbg(args...)  do { \
+	if (debug) { \
+		printk(KERN_DEBUG   "ITD1000: " args);\
+	} \
+} while (0)
+
+#define itd_warn(args...) do { \
+	printk(KERN_WARNING "ITD1000: " args); \
+} while (0)
+
+#define itd_info(args...) do { \
+	printk(KERN_INFO    "ITD1000: " args); \
+} while (0)
+
+/* don't write more than one byte with flexcop behind */
+static int itd1000_write_regs(struct itd1000_state *state, u8 reg, u8 v[], u8 len)
+{
+	u8 buf[MAX_XFER_SIZE];
+	struct i2c_msg msg = {
+		.addr = state->cfg->i2c_address, .flags = 0, .buf = buf, .len = len+1
+	};
+
+	if (1 + len > sizeof(buf)) {
+		printk(KERN_WARNING
+		       "itd1000: i2c wr reg=%04x: len=%d is too big!\n",
+		       reg, len);
+		return -EINVAL;
+	}
+
+	buf[0] = reg;
+	memcpy(&buf[1], v, len);
+
+	/* itd_dbg("wr %02x: %02x\n", reg, v[0]); */
+
+	if (i2c_transfer(state->i2c, &msg, 1) != 1) {
+		printk(KERN_WARNING "itd1000 I2C write failed\n");
+		return -EREMOTEIO;
+	}
+	return 0;
+}
+
+static int itd1000_read_reg(struct itd1000_state *state, u8 reg)
+{
+	u8 val;
+	struct i2c_msg msg[2] = {
+		{ .addr = state->cfg->i2c_address, .flags = 0,        .buf = &reg, .len = 1 },
+		{ .addr = state->cfg->i2c_address, .flags = I2C_M_RD, .buf = &val, .len = 1 },
+	};
+
+	/* ugly flexcop workaround */
+	itd1000_write_regs(state, (reg - 1) & 0xff, &state->shadow[(reg - 1) & 0xff], 1);
+
+	if (i2c_transfer(state->i2c, msg, 2) != 2) {
+		itd_warn("itd1000 I2C read failed\n");
+		return -EREMOTEIO;
+	}
+	return val;
+}
+
+static inline int itd1000_write_reg(struct itd1000_state *state, u8 r, u8 v)
+{
+	u8 tmp = v; /* see gcc.gnu.org/bugzilla/show_bug.cgi?id=81715 */
+	int ret = itd1000_write_regs(state, r, &tmp, 1);
+	state->shadow[r] = tmp;
+	return ret;
+}
+
+
+static struct {
+	u32 symbol_rate;
+	u8  pgaext  : 4; /* PLLFH */
+	u8  bbgvmin : 4; /* BBGVMIN */
+} itd1000_lpf_pga[] = {
+	{        0, 0x8, 0x3 },
+	{  5200000, 0x8, 0x3 },
+	{ 12200000, 0x4, 0x3 },
+	{ 15400000, 0x2, 0x3 },
+	{ 19800000, 0x2, 0x3 },
+	{ 21500000, 0x2, 0x3 },
+	{ 24500000, 0x2, 0x3 },
+	{ 28400000, 0x2, 0x3 },
+	{ 33400000, 0x2, 0x3 },
+	{ 34400000, 0x1, 0x4 },
+	{ 34400000, 0x1, 0x4 },
+	{ 38400000, 0x1, 0x4 },
+	{ 38400000, 0x1, 0x4 },
+	{ 40400000, 0x1, 0x4 },
+	{ 45400000, 0x1, 0x4 },
+};
+
+static void itd1000_set_lpf_bw(struct itd1000_state *state, u32 symbol_rate)
+{
+	u8 i;
+	u8 con1    = itd1000_read_reg(state, CON1)    & 0xfd;
+	u8 pllfh   = itd1000_read_reg(state, PLLFH)   & 0x0f;
+	u8 bbgvmin = itd1000_read_reg(state, BBGVMIN) & 0xf0;
+	u8 bw      = itd1000_read_reg(state, BW)      & 0xf0;
+
+	itd_dbg("symbol_rate = %d\n", symbol_rate);
+
+	/* not sure what is that ? - starting to download the table */
+	itd1000_write_reg(state, CON1, con1 | (1 << 1));
+
+	for (i = 0; i < ARRAY_SIZE(itd1000_lpf_pga); i++)
+		if (symbol_rate < itd1000_lpf_pga[i].symbol_rate) {
+			itd_dbg("symrate: index: %d pgaext: %x, bbgvmin: %x\n", i, itd1000_lpf_pga[i].pgaext, itd1000_lpf_pga[i].bbgvmin);
+			itd1000_write_reg(state, PLLFH,   pllfh | (itd1000_lpf_pga[i].pgaext << 4));
+			itd1000_write_reg(state, BBGVMIN, bbgvmin | (itd1000_lpf_pga[i].bbgvmin));
+			itd1000_write_reg(state, BW,      bw | (i & 0x0f));
+			break;
+		}
+
+	itd1000_write_reg(state, CON1, con1 | (0 << 1));
+}
+
+static struct {
+	u8 vcorg;
+	u32 fmax_rg;
+} itd1000_vcorg[] = {
+	{  1,  920000 },
+	{  2,  971000 },
+	{  3, 1031000 },
+	{  4, 1091000 },
+	{  5, 1171000 },
+	{  6, 1281000 },
+	{  7, 1381000 },
+	{  8,  500000 },	/* this is intentional. */
+	{  9, 1451000 },
+	{ 10, 1531000 },
+	{ 11, 1631000 },
+	{ 12, 1741000 },
+	{ 13, 1891000 },
+	{ 14, 2071000 },
+	{ 15, 2250000 },
+};
+
+static void itd1000_set_vco(struct itd1000_state *state, u32 freq_khz)
+{
+	u8 i;
+	u8 gvbb_i2c     = itd1000_read_reg(state, GVBB_I2C) & 0xbf;
+	u8 vco_chp1_i2c = itd1000_read_reg(state, VCO_CHP1_I2C) & 0x0f;
+	u8 adcout;
+
+	/* reserved bit again (reset ?) */
+	itd1000_write_reg(state, GVBB_I2C, gvbb_i2c | (1 << 6));
+
+	for (i = 0; i < ARRAY_SIZE(itd1000_vcorg); i++) {
+		if (freq_khz < itd1000_vcorg[i].fmax_rg) {
+			itd1000_write_reg(state, VCO_CHP1_I2C, vco_chp1_i2c | (itd1000_vcorg[i].vcorg << 4));
+			msleep(1);
+
+			adcout = itd1000_read_reg(state, PLLLOCK) & 0x0f;
+
+			itd_dbg("VCO: %dkHz: %d -> ADCOUT: %d %02x\n", freq_khz, itd1000_vcorg[i].vcorg, adcout, vco_chp1_i2c);
+
+			if (adcout > 13) {
+				if (!(itd1000_vcorg[i].vcorg == 7 || itd1000_vcorg[i].vcorg == 15))
+					itd1000_write_reg(state, VCO_CHP1_I2C, vco_chp1_i2c | ((itd1000_vcorg[i].vcorg + 1) << 4));
+			} else if (adcout < 2) {
+				if (!(itd1000_vcorg[i].vcorg == 1 || itd1000_vcorg[i].vcorg == 9))
+					itd1000_write_reg(state, VCO_CHP1_I2C, vco_chp1_i2c | ((itd1000_vcorg[i].vcorg - 1) << 4));
+			}
+			break;
+		}
+	}
+}
+
+static const struct {
+	u32 freq;
+	u8 values[10]; /* RFTR, RFST1 - RFST9 */
+} itd1000_fre_values[] = {
+	{ 1075000, { 0x59, 0x1d, 0x1c, 0x17, 0x16, 0x0f, 0x0e, 0x0c, 0x0b, 0x0a } },
+	{ 1250000, { 0x89, 0x1e, 0x1d, 0x17, 0x15, 0x0f, 0x0e, 0x0c, 0x0b, 0x0a } },
+	{ 1450000, { 0x89, 0x1e, 0x1d, 0x17, 0x15, 0x0f, 0x0e, 0x0c, 0x0b, 0x0a } },
+	{ 1650000, { 0x69, 0x1e, 0x1d, 0x17, 0x15, 0x0f, 0x0e, 0x0c, 0x0b, 0x0a } },
+	{ 1750000, { 0x69, 0x1e, 0x17, 0x15, 0x14, 0x0f, 0x0e, 0x0c, 0x0b, 0x0a } },
+	{ 1850000, { 0x69, 0x1d, 0x17, 0x16, 0x14, 0x0f, 0x0e, 0x0d, 0x0b, 0x0a } },
+	{ 1900000, { 0x69, 0x1d, 0x17, 0x15, 0x14, 0x0f, 0x0e, 0x0d, 0x0b, 0x0a } },
+	{ 1950000, { 0x69, 0x1d, 0x17, 0x16, 0x14, 0x13, 0x0e, 0x0d, 0x0b, 0x0a } },
+	{ 2050000, { 0x69, 0x1e, 0x1d, 0x17, 0x16, 0x14, 0x13, 0x0e, 0x0b, 0x0a } },
+	{ 2150000, { 0x69, 0x1d, 0x1c, 0x17, 0x15, 0x14, 0x13, 0x0f, 0x0e, 0x0b } }
+};
+
+
+#define FREF 16
+
+static void itd1000_set_lo(struct itd1000_state *state, u32 freq_khz)
+{
+	int i, j;
+	u32 plln, pllf;
+	u64 tmp;
+
+	plln = (freq_khz * 1000) / 2 / FREF;
+
+	/* Compute the factional part times 1000 */
+	tmp  = plln % 1000000;
+	plln /= 1000000;
+
+	tmp *= 1048576;
+	do_div(tmp, 1000000);
+	pllf = (u32) tmp;
+
+	state->frequency = ((plln * 1000) + (pllf * 1000)/1048576) * 2*FREF;
+	itd_dbg("frequency: %dkHz (wanted) %dkHz (set), PLLF = %d, PLLN = %d\n", freq_khz, state->frequency, pllf, plln);
+
+	itd1000_write_reg(state, PLLNH, 0x80); /* PLLNH */
+	itd1000_write_reg(state, PLLNL, plln & 0xff);
+	itd1000_write_reg(state, PLLFH, (itd1000_read_reg(state, PLLFH) & 0xf0) | ((pllf >> 16) & 0x0f));
+	itd1000_write_reg(state, PLLFM, (pllf >> 8) & 0xff);
+	itd1000_write_reg(state, PLLFL, (pllf >> 0) & 0xff);
+
+	for (i = 0; i < ARRAY_SIZE(itd1000_fre_values); i++) {
+		if (freq_khz <= itd1000_fre_values[i].freq) {
+			itd_dbg("fre_values: %d\n", i);
+			itd1000_write_reg(state, RFTR, itd1000_fre_values[i].values[0]);
+			for (j = 0; j < 9; j++)
+				itd1000_write_reg(state, RFST1+j, itd1000_fre_values[i].values[j+1]);
+			break;
+		}
+	}
+
+	itd1000_set_vco(state, freq_khz);
+}
+
+static int itd1000_set_parameters(struct dvb_frontend *fe)
+{
+	struct dtv_frontend_properties *c = &fe->dtv_property_cache;
+	struct itd1000_state *state = fe->tuner_priv;
+	u8 pllcon1;
+
+	itd1000_set_lo(state, c->frequency);
+	itd1000_set_lpf_bw(state, c->symbol_rate);
+
+	pllcon1 = itd1000_read_reg(state, PLLCON1) & 0x7f;
+	itd1000_write_reg(state, PLLCON1, pllcon1 | (1 << 7));
+	itd1000_write_reg(state, PLLCON1, pllcon1);
+
+	return 0;
+}
+
+static int itd1000_get_frequency(struct dvb_frontend *fe, u32 *frequency)
+{
+	struct itd1000_state *state = fe->tuner_priv;
+	*frequency = state->frequency;
+	return 0;
+}
+
+static int itd1000_get_bandwidth(struct dvb_frontend *fe, u32 *bandwidth)
+{
+	return 0;
+}
+
+static u8 itd1000_init_tab[][2] = {
+	{ PLLCON1,       0x65 }, /* Register does not change */
+	{ PLLNH,         0x80 }, /* Bits [7:6] do not change */
+	{ RESERVED_0X6D, 0x3b },
+	{ VCO_CHP2_I2C,  0x12 },
+	{ 0x72,          0xf9 }, /* No such regsister defined */
+	{ RESERVED_0X73, 0xff },
+	{ RESERVED_0X74, 0xb2 },
+	{ RESERVED_0X75, 0xc7 },
+	{ EXTGVBBRF,     0xf0 },
+	{ DIVAGCCK,      0x80 },
+	{ BBTR,          0xa0 },
+	{ RESERVED_0X7E, 0x4f },
+	{ 0x82,          0x88 }, /* No such regsister defined */
+	{ 0x83,          0x80 }, /* No such regsister defined */
+	{ 0x84,          0x80 }, /* No such regsister defined */
+	{ RESERVED_0X85, 0x74 },
+	{ RESERVED_0X86, 0xff },
+	{ RESERVED_0X88, 0x02 },
+	{ RESERVED_0X89, 0x16 },
+	{ RFST0,         0x1f },
+	{ RESERVED_0X94, 0x66 },
+	{ RESERVED_0X95, 0x66 },
+	{ RESERVED_0X96, 0x77 },
+	{ RESERVED_0X97, 0x99 },
+	{ RESERVED_0X98, 0xff },
+	{ RESERVED_0X99, 0xfc },
+	{ RESERVED_0X9A, 0xba },
+	{ RESERVED_0X9B, 0xaa },
+};
+
+static u8 itd1000_reinit_tab[][2] = {
+	{ VCO_CHP1_I2C, 0x8a },
+	{ BW,           0x87 },
+	{ GVBB_I2C,     0x03 },
+	{ BBGVMIN,      0x03 },
+	{ CON1,         0x2e },
+};
+
+
+static int itd1000_init(struct dvb_frontend *fe)
+{
+	struct itd1000_state *state = fe->tuner_priv;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(itd1000_init_tab); i++)
+		itd1000_write_reg(state, itd1000_init_tab[i][0], itd1000_init_tab[i][1]);
+
+	for (i = 0; i < ARRAY_SIZE(itd1000_reinit_tab); i++)
+		itd1000_write_reg(state, itd1000_reinit_tab[i][0], itd1000_reinit_tab[i][1]);
+
+	return 0;
+}
+
+static int itd1000_sleep(struct dvb_frontend *fe)
+{
+	return 0;
+}
+
+static void itd1000_release(struct dvb_frontend *fe)
+{
+	kfree(fe->tuner_priv);
+	fe->tuner_priv = NULL;
+}
+
+static const struct dvb_tuner_ops itd1000_tuner_ops = {
+	.info = {
+		.name              = "Integrant ITD1000",
+		.frequency_min_hz  =  950 * MHz,
+		.frequency_max_hz  = 2150 * MHz,
+		.frequency_step_hz =  125 * kHz,
+	},
+
+	.release       = itd1000_release,
+
+	.init          = itd1000_init,
+	.sleep         = itd1000_sleep,
+
+	.set_params    = itd1000_set_parameters,
+	.get_frequency = itd1000_get_frequency,
+	.get_bandwidth = itd1000_get_bandwidth
+};
+
+
+struct dvb_frontend *itd1000_attach(struct dvb_frontend *fe, struct i2c_adapter *i2c, struct itd1000_config *cfg)
+{
+	struct itd1000_state *state = NULL;
+	u8 i = 0;
+
+	state = kzalloc_obj(struct itd1000_state);
+	if (state == NULL)
+		return NULL;
+
+	state->cfg = cfg;
+	state->i2c = i2c;
+
+	i = itd1000_read_reg(state, 0);
+	if (i != 0) {
+		kfree(state);
+		return NULL;
+	}
+	itd_info("successfully identified (ID: %d)\n", i);
+
+	memset(state->shadow, 0xff, sizeof(state->shadow));
+	for (i = 0x65; i < 0x9c; i++)
+		state->shadow[i] = itd1000_read_reg(state, i);
+
+	memcpy(&fe->ops.tuner_ops, &itd1000_tuner_ops, sizeof(struct dvb_tuner_ops));
+
+	fe->tuner_priv = state;
+
+	return fe;
+}
+EXPORT_SYMBOL_GPL(itd1000_attach);
+
+MODULE_AUTHOR("Patrick Boettcher <pb@linuxtv.org>");
+MODULE_DESCRIPTION("Integrant ITD1000 driver");
+MODULE_LICENSE("GPL");