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, 442 insertions, 0 deletions

diff --git a/drivers/mfd/ipaq-micro.c b/drivers/mfd/ipaq-micro.c
new file mode 100644
index 000000000..5146a6eb0
--- /dev/null
+++ b/drivers/mfd/ipaq-micro.c
@@ -0,0 +1,442 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Compaq iPAQ h3xxx Atmel microcontroller companion support
+ *
+ * This is an Atmel AT90LS8535 with a special flashed-in firmware that
+ * implements the special protocol used by this driver.
+ *
+ * based on previous kernel 2.4 version by Andrew Christian
+ * Author : Alessandro Gardich <gremlin@gremlin.it>
+ * Author : Dmitry Artamonow <mad_soft@inbox.ru>
+ * Author : Linus Walleij <linus.walleij@linaro.org>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/pm.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/io.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/ipaq-micro.h>
+#include <linux/string.h>
+#include <linux/string_choices.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+
+#include <mach/hardware.h>
+
+static void ipaq_micro_trigger_tx(struct ipaq_micro *micro)
+{
+	struct ipaq_micro_txdev *tx = &micro->tx;
+	struct ipaq_micro_msg *msg = micro->msg;
+	int i, bp;
+	u8 checksum;
+	u32 val;
+
+	bp = 0;
+	tx->buf[bp++] = CHAR_SOF;
+
+	checksum = ((msg->id & 0x0f) << 4) | (msg->tx_len & 0x0f);
+	tx->buf[bp++] = checksum;
+
+	for (i = 0; i < msg->tx_len; i++) {
+		tx->buf[bp++] = msg->tx_data[i];
+		checksum += msg->tx_data[i];
+	}
+
+	tx->buf[bp++] = checksum;
+	tx->len = bp;
+	tx->index = 0;
+
+	/* Enable interrupt */
+	val = readl(micro->base + UTCR3);
+	val |= UTCR3_TIE;
+	writel(val, micro->base + UTCR3);
+}
+
+int ipaq_micro_tx_msg(struct ipaq_micro *micro, struct ipaq_micro_msg *msg)
+{
+	unsigned long flags;
+
+	dev_dbg(micro->dev, "TX msg: %02x, %d bytes\n", msg->id, msg->tx_len);
+
+	spin_lock_irqsave(&micro->lock, flags);
+	if (micro->msg) {
+		list_add_tail(&msg->node, &micro->queue);
+		spin_unlock_irqrestore(&micro->lock, flags);
+		return 0;
+	}
+	micro->msg = msg;
+	ipaq_micro_trigger_tx(micro);
+	spin_unlock_irqrestore(&micro->lock, flags);
+	return 0;
+}
+EXPORT_SYMBOL(ipaq_micro_tx_msg);
+
+static void micro_rx_msg(struct ipaq_micro *micro, u8 id, int len, u8 *data)
+{
+	dev_dbg(micro->dev, "RX msg: %02x, %d bytes\n", id, len);
+
+	spin_lock(&micro->lock);
+	switch (id) {
+	case MSG_VERSION:
+	case MSG_EEPROM_READ:
+	case MSG_EEPROM_WRITE:
+	case MSG_BACKLIGHT:
+	case MSG_NOTIFY_LED:
+	case MSG_THERMAL_SENSOR:
+	case MSG_BATTERY:
+		/* Handle synchronous messages */
+		if (micro->msg && micro->msg->id == id) {
+			struct ipaq_micro_msg *msg = micro->msg;
+
+			memcpy(msg->rx_data, data, len);
+			msg->rx_len = len;
+			complete(&micro->msg->ack);
+			if (!list_empty(&micro->queue)) {
+				micro->msg = list_entry(micro->queue.next,
+							struct ipaq_micro_msg,
+							node);
+				list_del_init(&micro->msg->node);
+				ipaq_micro_trigger_tx(micro);
+			} else
+				micro->msg = NULL;
+			dev_dbg(micro->dev, "OK RX message 0x%02x\n", id);
+		} else {
+			dev_err(micro->dev,
+				"out of band RX message 0x%02x\n", id);
+			if (!micro->msg)
+				dev_info(micro->dev, "no message queued\n");
+			else
+				dev_info(micro->dev, "expected message %02x\n",
+					 micro->msg->id);
+		}
+		break;
+	case MSG_KEYBOARD:
+		if (micro->key)
+			micro->key(micro->key_data, len, data);
+		else
+			dev_dbg(micro->dev, "key message ignored, no handle\n");
+		break;
+	case MSG_TOUCHSCREEN:
+		if (micro->ts)
+			micro->ts(micro->ts_data, len, data);
+		else
+			dev_dbg(micro->dev, "touchscreen message ignored, no handle\n");
+		break;
+	default:
+		dev_err(micro->dev,
+			"unknown msg %d [%d] %*ph\n", id, len, len, data);
+		break;
+	}
+	spin_unlock(&micro->lock);
+}
+
+static void micro_process_char(struct ipaq_micro *micro, u8 ch)
+{
+	struct ipaq_micro_rxdev *rx = &micro->rx;
+
+	switch (rx->state) {
+	case STATE_SOF:	/* Looking for SOF */
+		if (ch == CHAR_SOF)
+			rx->state = STATE_ID; /* Next byte is the id and len */
+		break;
+	case STATE_ID: /* Looking for id and len byte */
+		rx->id = (ch & 0xf0) >> 4;
+		rx->len = (ch & 0x0f);
+		rx->index = 0;
+		rx->chksum = ch;
+		rx->state = (rx->len > 0) ? STATE_DATA : STATE_CHKSUM;
+		break;
+	case STATE_DATA: /* Looking for 'len' data bytes */
+		rx->chksum += ch;
+		rx->buf[rx->index] = ch;
+		if (++rx->index == rx->len)
+			rx->state = STATE_CHKSUM;
+		break;
+	case STATE_CHKSUM: /* Looking for the checksum */
+		if (ch == rx->chksum)
+			micro_rx_msg(micro, rx->id, rx->len, rx->buf);
+		rx->state = STATE_SOF;
+		break;
+	}
+}
+
+static void micro_rx_chars(struct ipaq_micro *micro)
+{
+	u32 status, ch;
+
+	while ((status = readl(micro->base + UTSR1)) & UTSR1_RNE) {
+		ch = readl(micro->base + UTDR);
+		if (status & UTSR1_PRE)
+			dev_err(micro->dev, "rx: parity error\n");
+		else if (status & UTSR1_FRE)
+			dev_err(micro->dev, "rx: framing error\n");
+		else if (status & UTSR1_ROR)
+			dev_err(micro->dev, "rx: overrun error\n");
+		micro_process_char(micro, ch);
+	}
+}
+
+static void ipaq_micro_get_version(struct ipaq_micro *micro)
+{
+	struct ipaq_micro_msg msg = {
+		.id = MSG_VERSION,
+	};
+
+	ipaq_micro_tx_msg_sync(micro, &msg);
+	if (msg.rx_len == 4) {
+		memcpy(micro->version, msg.rx_data, 4);
+		micro->version[4] = '\0';
+	} else if (msg.rx_len == 9) {
+		memcpy(micro->version, msg.rx_data, 4);
+		micro->version[4] = '\0';
+		/* Bytes 4-7 are "pack", byte 8 is "boot type" */
+	} else {
+		dev_err(micro->dev,
+			"illegal version message %d bytes\n", msg.rx_len);
+	}
+}
+
+static void ipaq_micro_eeprom_read(struct ipaq_micro *micro,
+				   u8 address, u8 len, u8 *data)
+{
+	struct ipaq_micro_msg msg = {
+		.id = MSG_EEPROM_READ,
+	};
+	u8 i;
+
+	for (i = 0; i < len; i++) {
+		msg.tx_data[0] = address + i;
+		msg.tx_data[1] = 1;
+		msg.tx_len = 2;
+		ipaq_micro_tx_msg_sync(micro, &msg);
+		memcpy(data + (i * 2), msg.rx_data, 2);
+	}
+}
+
+static char *ipaq_micro_str(u8 *wchar, u8 len)
+{
+	char retstr[256] = { 0 };
+	u8 i;
+
+	for (i = 0; i < len / 2; i++)
+		retstr[i] = wchar[i * 2];
+	return kstrdup(retstr, GFP_KERNEL);
+}
+
+static u16 ipaq_micro_to_u16(u8 *data)
+{
+	return data[1] << 8 | data[0];
+}
+
+static void __init ipaq_micro_eeprom_dump(struct ipaq_micro *micro)
+{
+	u8 dump[256];
+	char *str;
+
+	ipaq_micro_eeprom_read(micro, 0, 128, dump);
+	str = ipaq_micro_str(dump, 10);
+	if (str) {
+		dev_info(micro->dev, "HW version %s\n", str);
+		kfree(str);
+	}
+	str = ipaq_micro_str(dump+10, 40);
+	if (str) {
+		dev_info(micro->dev, "serial number: %s\n", str);
+		/* Feed the random pool with this */
+		add_device_randomness(str, strlen(str));
+		kfree(str);
+	}
+	str = ipaq_micro_str(dump+50, 20);
+	if (str) {
+		dev_info(micro->dev, "module ID: %s\n", str);
+		kfree(str);
+	}
+	str = ipaq_micro_str(dump+70, 10);
+	if (str) {
+		dev_info(micro->dev, "product revision: %s\n", str);
+		kfree(str);
+	}
+	dev_info(micro->dev, "product ID: %u\n", ipaq_micro_to_u16(dump+80));
+	dev_info(micro->dev, "frame rate: %u fps\n",
+		 ipaq_micro_to_u16(dump+82));
+	dev_info(micro->dev, "page mode: %u\n", ipaq_micro_to_u16(dump+84));
+	dev_info(micro->dev, "country ID: %u\n", ipaq_micro_to_u16(dump+86));
+	dev_info(micro->dev, "color display: %s\n",
+		 str_yes_no(ipaq_micro_to_u16(dump + 88)));
+	dev_info(micro->dev, "ROM size: %u MiB\n", ipaq_micro_to_u16(dump+90));
+	dev_info(micro->dev, "RAM size: %u KiB\n", ipaq_micro_to_u16(dump+92));
+	dev_info(micro->dev, "screen: %u x %u\n",
+		 ipaq_micro_to_u16(dump+94), ipaq_micro_to_u16(dump+96));
+}
+
+static void micro_tx_chars(struct ipaq_micro *micro)
+{
+	struct ipaq_micro_txdev *tx = &micro->tx;
+	u32 val;
+
+	while ((tx->index < tx->len) &&
+	       (readl(micro->base + UTSR1) & UTSR1_TNF)) {
+		writel(tx->buf[tx->index], micro->base + UTDR);
+		tx->index++;
+	}
+
+	/* Stop interrupts */
+	val = readl(micro->base + UTCR3);
+	val &= ~UTCR3_TIE;
+	writel(val, micro->base + UTCR3);
+}
+
+static void micro_reset_comm(struct ipaq_micro *micro)
+{
+	struct ipaq_micro_rxdev *rx = &micro->rx;
+	u32 val;
+
+	if (micro->msg)
+		complete(&micro->msg->ack);
+
+	/* Initialize Serial channel protocol frame */
+	rx->state = STATE_SOF;  /* Reset the state machine */
+
+	/* Set up interrupts */
+	writel(0x01, micro->sdlc + 0x0); /* Select UART mode */
+
+	/* Clean up CR3 */
+	writel(0x0, micro->base + UTCR3);
+
+	/* Format: 8N1 */
+	writel(UTCR0_8BitData | UTCR0_1StpBit, micro->base + UTCR0);
+
+	/* Baud rate: 115200 */
+	writel(0x0, micro->base + UTCR1);
+	writel(0x1, micro->base + UTCR2);
+
+	/* Clear SR0 */
+	writel(0xff, micro->base + UTSR0);
+
+	/* Enable RX int, disable TX int */
+	writel(UTCR3_TXE | UTCR3_RXE | UTCR3_RIE, micro->base + UTCR3);
+	val = readl(micro->base + UTCR3);
+	val &= ~UTCR3_TIE;
+	writel(val, micro->base + UTCR3);
+}
+
+static irqreturn_t micro_serial_isr(int irq, void *dev_id)
+{
+	struct ipaq_micro *micro = dev_id;
+	struct ipaq_micro_txdev *tx = &micro->tx;
+	u32 status;
+
+	status = readl(micro->base + UTSR0);
+	do {
+		if (status & (UTSR0_RID | UTSR0_RFS)) {
+			if (status & UTSR0_RID)
+				/* Clear the Receiver IDLE bit */
+				writel(UTSR0_RID, micro->base + UTSR0);
+			micro_rx_chars(micro);
+		}
+
+		/* Clear break bits */
+		if (status & (UTSR0_RBB | UTSR0_REB))
+			writel(status & (UTSR0_RBB | UTSR0_REB),
+			       micro->base + UTSR0);
+
+		if (status & UTSR0_TFS)
+			micro_tx_chars(micro);
+
+		status = readl(micro->base + UTSR0);
+
+	} while (((tx->index < tx->len) && (status & UTSR0_TFS)) ||
+		 (status & (UTSR0_RFS | UTSR0_RID)));
+
+	return IRQ_HANDLED;
+}
+
+static const struct mfd_cell micro_cells[] = {
+	{ .name = "ipaq-micro-backlight", },
+	{ .name = "ipaq-micro-battery", },
+	{ .name = "ipaq-micro-keys", },
+	{ .name = "ipaq-micro-ts", },
+	{ .name = "ipaq-micro-leds", },
+};
+
+static int __maybe_unused micro_resume(struct device *dev)
+{
+	struct ipaq_micro *micro = dev_get_drvdata(dev);
+
+	micro_reset_comm(micro);
+	mdelay(10);
+
+	return 0;
+}
+
+static int __init micro_probe(struct platform_device *pdev)
+{
+	struct ipaq_micro *micro;
+	int ret;
+	int irq;
+
+	micro = devm_kzalloc(&pdev->dev, sizeof(*micro), GFP_KERNEL);
+	if (!micro)
+		return -ENOMEM;
+
+	micro->dev = &pdev->dev;
+
+	micro->base = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
+	if (IS_ERR(micro->base))
+		return PTR_ERR(micro->base);
+
+	micro->sdlc = devm_platform_ioremap_resource(pdev, 1);
+	if (IS_ERR(micro->sdlc))
+		return PTR_ERR(micro->sdlc);
+
+	micro_reset_comm(micro);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return -EINVAL;
+	ret = devm_request_irq(&pdev->dev, irq, micro_serial_isr,
+			       IRQF_SHARED, "ipaq-micro",
+			       micro);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to grab serial port IRQ\n");
+		return ret;
+	} else
+		dev_info(&pdev->dev, "grabbed serial port IRQ\n");
+
+	spin_lock_init(&micro->lock);
+	INIT_LIST_HEAD(&micro->queue);
+	platform_set_drvdata(pdev, micro);
+
+	ret = mfd_add_devices(&pdev->dev, pdev->id, micro_cells,
+			      ARRAY_SIZE(micro_cells), NULL, 0, NULL);
+	if (ret) {
+		dev_err(&pdev->dev, "error adding MFD cells");
+		return ret;
+	}
+
+	/* Check version */
+	ipaq_micro_get_version(micro);
+	dev_info(&pdev->dev, "Atmel micro ASIC version %s\n", micro->version);
+	ipaq_micro_eeprom_dump(micro);
+
+	return 0;
+}
+
+static const struct dev_pm_ops micro_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(NULL, micro_resume)
+};
+
+static struct platform_driver micro_device_driver = {
+	.driver   = {
+		.name	= "ipaq-h3xxx-micro",
+		.pm	= &micro_dev_pm_ops,
+		.suppress_bind_attrs = true,
+	},
+};
+builtin_platform_driver_probe(micro_device_driver, micro_probe);