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, 339 insertions, 0 deletions

diff --git a/drivers/nfc/pn533/uart.c b/drivers/nfc/pn533/uart.c
new file mode 100644
index 000000000..83c1ccda0
--- /dev/null
+++ b/drivers/nfc/pn533/uart.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Driver for NXP PN532 NFC Chip - UART transport layer
+ *
+ * Copyright (C) 2018 Lemonage Software GmbH
+ * Author: Lars Pöschel <poeschel@lemonage.de>
+ * All rights reserved.
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/nfc.h>
+#include <linux/netdevice.h>
+#include <linux/of.h>
+#include <linux/serdev.h>
+#include "pn533.h"
+
+#define PN532_UART_SKB_BUFF_LEN	(PN533_CMD_DATAEXCH_DATA_MAXLEN * 2)
+
+enum send_wakeup {
+	PN532_SEND_NO_WAKEUP = 0,
+	PN532_SEND_WAKEUP,
+	PN532_SEND_LAST_WAKEUP,
+};
+
+
+struct pn532_uart_phy {
+	struct serdev_device *serdev;
+	struct sk_buff *recv_skb;
+	struct pn533 *priv;
+	/*
+	 * send_wakeup variable is used to control if we need to send a wakeup
+	 * request to the pn532 chip prior to our actual command. There is a
+	 * little propability of a race condition. We decided to not mutex the
+	 * variable as the worst that could happen is, that we send a wakeup
+	 * to the chip that is already awake. This does not hurt. It is a
+	 * no-op to the chip.
+	 */
+	enum send_wakeup send_wakeup;
+	struct timer_list cmd_timeout;
+	struct sk_buff *cur_out_buf;
+};
+
+static int pn532_uart_send_frame(struct pn533 *dev,
+				struct sk_buff *out)
+{
+	/* wakeup sequence and dummy bytes for waiting time */
+	static const u8 wakeup[] = {
+		0x55, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
+	struct pn532_uart_phy *pn532 = dev->phy;
+	int err;
+
+	print_hex_dump_debug("PN532_uart TX: ", DUMP_PREFIX_NONE, 16, 1,
+			     out->data, out->len, false);
+
+	pn532->cur_out_buf = out;
+	if (pn532->send_wakeup) {
+		err = serdev_device_write(pn532->serdev,
+				wakeup, sizeof(wakeup),
+				MAX_SCHEDULE_TIMEOUT);
+		if (err < 0)
+			return err;
+	}
+
+	if (pn532->send_wakeup == PN532_SEND_LAST_WAKEUP)
+		pn532->send_wakeup = PN532_SEND_NO_WAKEUP;
+
+	err = serdev_device_write(pn532->serdev, out->data, out->len,
+			MAX_SCHEDULE_TIMEOUT);
+	if (err < 0)
+		return err;
+
+	mod_timer(&pn532->cmd_timeout, HZ / 40 + jiffies);
+	return 0;
+}
+
+static int pn532_uart_send_ack(struct pn533 *dev, gfp_t flags)
+{
+	/* spec 7.1.1.3:  Preamble, SoPC (2), ACK Code (2), Postamble */
+	static const u8 ack[PN533_STD_FRAME_ACK_SIZE] = {
+			0x00, 0x00, 0xff, 0x00, 0xff, 0x00};
+	struct pn532_uart_phy *pn532 = dev->phy;
+	int err;
+
+	err = serdev_device_write(pn532->serdev, ack, sizeof(ack),
+			MAX_SCHEDULE_TIMEOUT);
+	if (err < 0)
+		return err;
+
+	return 0;
+}
+
+static void pn532_uart_abort_cmd(struct pn533 *dev, gfp_t flags)
+{
+	/* An ack will cancel the last issued command */
+	pn532_uart_send_ack(dev, flags);
+	/* schedule cmd_complete_work to finish current command execution */
+	pn533_recv_frame(dev, NULL, -ENOENT);
+}
+
+static int pn532_dev_up(struct pn533 *dev)
+{
+	struct pn532_uart_phy *pn532 = dev->phy;
+	int ret = 0;
+
+	ret = serdev_device_open(pn532->serdev);
+	if (ret)
+		return ret;
+
+	pn532->send_wakeup = PN532_SEND_LAST_WAKEUP;
+	return ret;
+}
+
+static int pn532_dev_down(struct pn533 *dev)
+{
+	struct pn532_uart_phy *pn532 = dev->phy;
+
+	serdev_device_close(pn532->serdev);
+	pn532->send_wakeup = PN532_SEND_WAKEUP;
+
+	return 0;
+}
+
+static const struct pn533_phy_ops uart_phy_ops = {
+	.send_frame = pn532_uart_send_frame,
+	.send_ack = pn532_uart_send_ack,
+	.abort_cmd = pn532_uart_abort_cmd,
+	.dev_up = pn532_dev_up,
+	.dev_down = pn532_dev_down,
+};
+
+static void pn532_cmd_timeout(struct timer_list *t)
+{
+	struct pn532_uart_phy *dev = timer_container_of(dev, t, cmd_timeout);
+
+	pn532_uart_send_frame(dev->priv, dev->cur_out_buf);
+}
+
+/*
+ * scans the buffer if it contains a pn532 frame. It is not checked if the
+ * frame is really valid. This is later done with pn533_rx_frame_is_valid.
+ * This is useful for malformed or errornous transmitted frames. Adjusts the
+ * bufferposition where the frame starts, since pn533_recv_frame expects a
+ * well formed frame.
+ */
+static int pn532_uart_rx_is_frame(struct sk_buff *skb)
+{
+	struct pn533_std_frame *std;
+	struct pn533_ext_frame *ext;
+	u16 frame_len;
+	int i;
+
+	for (i = 0; i + PN533_STD_FRAME_ACK_SIZE <= skb->len; i++) {
+		std = (struct pn533_std_frame *)&skb->data[i];
+		/* search start code */
+		if (std->start_frame != cpu_to_be16(PN533_STD_FRAME_SOF))
+			continue;
+
+		/* frame type */
+		switch (std->datalen) {
+		case PN533_FRAME_DATALEN_ACK:
+			if (std->datalen_checksum == 0xff) {
+				skb_pull(skb, i);
+				return 1;
+			}
+
+			break;
+		case PN533_FRAME_DATALEN_ERROR:
+			if ((std->datalen_checksum == 0xff) &&
+					(skb->len >=
+					 PN533_STD_ERROR_FRAME_SIZE)) {
+				skb_pull(skb, i);
+				return 1;
+			}
+
+			break;
+		case PN533_FRAME_DATALEN_EXTENDED:
+			ext = (struct pn533_ext_frame *)&skb->data[i];
+			frame_len = be16_to_cpu(ext->datalen);
+			if (skb->len >= frame_len +
+					sizeof(struct pn533_ext_frame) +
+					2 /* CKS + Postamble */) {
+				skb_pull(skb, i);
+				return 1;
+			}
+
+			break;
+		default: /* normal information frame */
+			frame_len = std->datalen;
+			if (skb->len >= frame_len +
+					sizeof(struct pn533_std_frame) +
+					2 /* CKS + Postamble */) {
+				skb_pull(skb, i);
+				return 1;
+			}
+
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static size_t pn532_receive_buf(struct serdev_device *serdev,
+				const u8 *data, size_t count)
+{
+	struct pn532_uart_phy *dev = serdev_device_get_drvdata(serdev);
+	size_t i;
+
+	timer_delete(&dev->cmd_timeout);
+	for (i = 0; i < count; i++) {
+		if (!dev->recv_skb) {
+			dev->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN,
+						  GFP_KERNEL);
+			if (!dev->recv_skb)
+				return i;
+		}
+
+		if (unlikely(!skb_tailroom(dev->recv_skb)))
+			skb_trim(dev->recv_skb, 0);
+
+		skb_put_u8(dev->recv_skb, *data++);
+		if (!pn532_uart_rx_is_frame(dev->recv_skb))
+			continue;
+
+		pn533_recv_frame(dev->priv, dev->recv_skb, 0);
+		dev->recv_skb = NULL;
+	}
+
+	return i;
+}
+
+static const struct serdev_device_ops pn532_serdev_ops = {
+	.receive_buf = pn532_receive_buf,
+	.write_wakeup = serdev_device_write_wakeup,
+};
+
+static const struct of_device_id pn532_uart_of_match[] = {
+	{ .compatible = "nxp,pn532" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, pn532_uart_of_match);
+
+static int pn532_uart_probe(struct serdev_device *serdev)
+{
+	struct pn532_uart_phy *pn532;
+	struct pn533 *priv;
+	int err;
+
+	err = -ENOMEM;
+	pn532 = kzalloc_obj(*pn532);
+	if (!pn532)
+		goto err_exit;
+
+	pn532->recv_skb = alloc_skb(PN532_UART_SKB_BUFF_LEN, GFP_KERNEL);
+	if (!pn532->recv_skb)
+		goto err_free;
+
+	pn532->serdev = serdev;
+	serdev_device_set_drvdata(serdev, pn532);
+	serdev_device_set_client_ops(serdev, &pn532_serdev_ops);
+	err = serdev_device_open(serdev);
+	if (err) {
+		dev_err(&serdev->dev, "Unable to open device\n");
+		goto err_skb;
+	}
+
+	err = serdev_device_set_baudrate(serdev, 115200);
+	if (err != 115200) {
+		err = -EINVAL;
+		goto err_serdev;
+	}
+
+	serdev_device_set_flow_control(serdev, false);
+	pn532->send_wakeup = PN532_SEND_WAKEUP;
+	timer_setup(&pn532->cmd_timeout, pn532_cmd_timeout, 0);
+	priv = pn53x_common_init(PN533_DEVICE_PN532_AUTOPOLL,
+				     PN533_PROTO_REQ_ACK_RESP,
+				     pn532, &uart_phy_ops, NULL,
+				     &pn532->serdev->dev);
+	if (IS_ERR(priv)) {
+		err = PTR_ERR(priv);
+		goto err_serdev;
+	}
+
+	pn532->priv = priv;
+	err = pn533_finalize_setup(pn532->priv);
+	if (err)
+		goto err_clean;
+
+	serdev_device_close(serdev);
+	err = pn53x_register_nfc(priv, PN533_NO_TYPE_B_PROTOCOLS, &serdev->dev);
+	if (err) {
+		pn53x_common_clean(pn532->priv);
+		goto err_skb;
+	}
+
+	return err;
+
+err_clean:
+	pn53x_common_clean(pn532->priv);
+err_serdev:
+	serdev_device_close(serdev);
+err_skb:
+	kfree_skb(pn532->recv_skb);
+err_free:
+	kfree(pn532);
+err_exit:
+	return err;
+}
+
+static void pn532_uart_remove(struct serdev_device *serdev)
+{
+	struct pn532_uart_phy *pn532 = serdev_device_get_drvdata(serdev);
+
+	pn53x_unregister_nfc(pn532->priv);
+	serdev_device_close(serdev);
+	pn53x_common_clean(pn532->priv);
+	timer_shutdown_sync(&pn532->cmd_timeout);
+	kfree_skb(pn532->recv_skb);
+	kfree(pn532);
+}
+
+static struct serdev_device_driver pn532_uart_driver = {
+	.probe = pn532_uart_probe,
+	.remove = pn532_uart_remove,
+	.driver = {
+		.name = "pn532_uart",
+		.of_match_table = pn532_uart_of_match,
+	},
+};
+
+module_serdev_device_driver(pn532_uart_driver);
+
+MODULE_AUTHOR("Lars Pöschel <poeschel@lemonage.de>");
+MODULE_DESCRIPTION("PN532 UART driver");
+MODULE_LICENSE("GPL");