From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions 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) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/bluetooth/hci_serdev.c | 414 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 414 insertions(+) create mode 100644 drivers/bluetooth/hci_serdev.c (limited to 'drivers/bluetooth/hci_serdev.c') diff --git a/drivers/bluetooth/hci_serdev.c b/drivers/bluetooth/hci_serdev.c new file mode 100644 index 000000000..d2eaf2f12 --- /dev/null +++ b/drivers/bluetooth/hci_serdev.c @@ -0,0 +1,414 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Bluetooth HCI serdev driver lib + * + * Copyright (C) 2017 Linaro, Ltd., Rob Herring + * + * Based on hci_ldisc.c: + * + * Copyright (C) 2000-2001 Qualcomm Incorporated + * Copyright (C) 2002-2003 Maxim Krasnyansky + * Copyright (C) 2004-2005 Marcel Holtmann + */ + +#include +#include +#include +#include + +#include +#include + +#include "hci_uart.h" + +static inline void hci_uart_tx_complete(struct hci_uart *hu, int pkt_type) +{ + struct hci_dev *hdev = hu->hdev; + + /* Update HCI stat counters */ + switch (pkt_type) { + case HCI_COMMAND_PKT: + hdev->stat.cmd_tx++; + break; + + case HCI_ACLDATA_PKT: + hdev->stat.acl_tx++; + break; + + case HCI_SCODATA_PKT: + hdev->stat.sco_tx++; + break; + } +} + +static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu) +{ + struct sk_buff *skb = hu->tx_skb; + + if (!skb) { + if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) + skb = hu->proto->dequeue(hu); + } else + hu->tx_skb = NULL; + + return skb; +} + +static void hci_uart_write_work(struct work_struct *work) +{ + struct hci_uart *hu = container_of(work, struct hci_uart, write_work); + struct serdev_device *serdev = hu->serdev; + struct hci_dev *hdev = hu->hdev; + struct sk_buff *skb; + + /* REVISIT: + * should we cope with bad skbs or ->write() returning an error value? + */ + do { + clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); + + while ((skb = hci_uart_dequeue(hu))) { + int len; + + len = serdev_device_write_buf(serdev, + skb->data, skb->len); + hdev->stat.byte_tx += len; + + skb_pull(skb, len); + if (skb->len) { + hu->tx_skb = skb; + break; + } + + hci_uart_tx_complete(hu, hci_skb_pkt_type(skb)); + kfree_skb(skb); + } + + clear_bit(HCI_UART_SENDING, &hu->tx_state); + } while (test_bit(HCI_UART_TX_WAKEUP, &hu->tx_state)); +} + +/* ------- Interface to HCI layer ------ */ + +/* Reset device */ +static int hci_uart_flush(struct hci_dev *hdev) +{ + struct hci_uart *hu = hci_get_drvdata(hdev); + + BT_DBG("hdev %p serdev %p", hdev, hu->serdev); + + if (hu->tx_skb) { + kfree_skb(hu->tx_skb); hu->tx_skb = NULL; + } + + /* Flush any pending characters in the driver and discipline. */ + serdev_device_write_flush(hu->serdev); + + if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) + hu->proto->flush(hu); + + return 0; +} + +/* Initialize device */ +static int hci_uart_open(struct hci_dev *hdev) +{ + struct hci_uart *hu = hci_get_drvdata(hdev); + int err; + + BT_DBG("%s %p", hdev->name, hdev); + + /* When Quirk HCI_QUIRK_NON_PERSISTENT_SETUP is set by + * driver, BT SoC is completely turned OFF during + * BT OFF. Upon next BT ON UART port should be opened. + */ + if (!test_bit(HCI_UART_PROTO_READY, &hu->flags)) { + err = serdev_device_open(hu->serdev); + if (err) + return err; + set_bit(HCI_UART_PROTO_READY, &hu->flags); + } + + /* Undo clearing this from hci_uart_close() */ + hdev->flush = hci_uart_flush; + + return 0; +} + +/* Close device */ +static int hci_uart_close(struct hci_dev *hdev) +{ + struct hci_uart *hu = hci_get_drvdata(hdev); + + BT_DBG("hdev %p", hdev); + + if (!test_bit(HCI_UART_PROTO_READY, &hu->flags)) + return 0; + + hci_uart_flush(hdev); + hdev->flush = NULL; + + /* When QUIRK HCI_QUIRK_NON_PERSISTENT_SETUP is set by driver, + * BT SOC is completely powered OFF during BT OFF, holding port + * open may drain the battery. + */ + if (hci_test_quirk(hdev, HCI_QUIRK_NON_PERSISTENT_SETUP)) { + clear_bit(HCI_UART_PROTO_READY, &hu->flags); + serdev_device_close(hu->serdev); + } + + return 0; +} + +/* Send frames from HCI layer */ +static int hci_uart_send_frame(struct hci_dev *hdev, struct sk_buff *skb) +{ + struct hci_uart *hu = hci_get_drvdata(hdev); + + BT_DBG("%s: type %d len %d", hdev->name, hci_skb_pkt_type(skb), + skb->len); + + hu->proto->enqueue(hu, skb); + + hci_uart_tx_wakeup(hu); + + return 0; +} + +static int hci_uart_setup(struct hci_dev *hdev) +{ + struct hci_uart *hu = hci_get_drvdata(hdev); + struct hci_rp_read_local_version *ver; + struct sk_buff *skb; + unsigned int speed; + int err; + + /* Init speed if any */ + if (hu->init_speed) + speed = hu->init_speed; + else if (hu->proto->init_speed) + speed = hu->proto->init_speed; + else + speed = 0; + + if (speed) + serdev_device_set_baudrate(hu->serdev, speed); + + /* Operational speed if any */ + if (hu->oper_speed) + speed = hu->oper_speed; + else if (hu->proto->oper_speed) + speed = hu->proto->oper_speed; + else + speed = 0; + + if (hu->proto->set_baudrate && speed) { + err = hu->proto->set_baudrate(hu, speed); + if (err) + bt_dev_err(hdev, "Failed to set baudrate"); + else + serdev_device_set_baudrate(hu->serdev, speed); + } + + if (hu->proto->setup) + return hu->proto->setup(hu); + + if (!test_bit(HCI_UART_VND_DETECT, &hu->hdev_flags)) + return 0; + + skb = __hci_cmd_sync(hdev, HCI_OP_READ_LOCAL_VERSION, 0, NULL, + HCI_INIT_TIMEOUT); + if (IS_ERR(skb)) { + bt_dev_err(hdev, "Reading local version info failed (%ld)", + PTR_ERR(skb)); + return PTR_ERR(skb); + } + + if (skb->len != sizeof(*ver)) + bt_dev_err(hdev, "Event length mismatch for version info"); + + kfree_skb(skb); + return 0; +} + +/* Check if the device is wakeable */ +static bool hci_uart_wakeup(struct hci_dev *hdev) +{ + /* HCI UART devices are assumed to be wakeable by default. + * Implement wakeup callback to override this behavior. + */ + return true; +} + +/** hci_uart_write_wakeup - transmit buffer wakeup + * @serdev: serial device + * + * This function is called by the serdev framework when it accepts + * more data being sent. + */ +static void hci_uart_write_wakeup(struct serdev_device *serdev) +{ + struct hci_uart *hu = serdev_device_get_drvdata(serdev); + + BT_DBG(""); + + if (!hu || serdev != hu->serdev) { + WARN_ON(1); + return; + } + + if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) + hci_uart_tx_wakeup(hu); +} + +/** hci_uart_receive_buf - receive buffer wakeup + * @serdev: serial device + * @data: pointer to received data + * @count: count of received data in bytes + * + * This function is called by the serdev framework when it received data + * in the RX buffer. + * + * Return: number of processed bytes + */ +static size_t hci_uart_receive_buf(struct serdev_device *serdev, + const u8 *data, size_t count) +{ + struct hci_uart *hu = serdev_device_get_drvdata(serdev); + + if (!hu || serdev != hu->serdev) { + WARN_ON(1); + return 0; + } + + if (!test_bit(HCI_UART_PROTO_READY, &hu->flags)) + return 0; + + /* It does not need a lock here as it is already protected by a mutex in + * tty caller + */ + hu->proto->recv(hu, data, count); + + if (hu->hdev) + hu->hdev->stat.byte_rx += count; + + return count; +} + +static const struct serdev_device_ops hci_serdev_client_ops = { + .receive_buf = hci_uart_receive_buf, + .write_wakeup = hci_uart_write_wakeup, +}; + +int hci_uart_register_device_priv(struct hci_uart *hu, + const struct hci_uart_proto *p, + int sizeof_priv) +{ + int err; + struct hci_dev *hdev; + + BT_DBG(""); + + serdev_device_set_client_ops(hu->serdev, &hci_serdev_client_ops); + + if (percpu_init_rwsem(&hu->proto_lock)) + return -ENOMEM; + + err = serdev_device_open(hu->serdev); + if (err) + goto err_rwsem; + + err = p->open(hu); + if (err) + goto err_open; + + hu->proto = p; + set_bit(HCI_UART_PROTO_READY, &hu->flags); + + /* Initialize and register HCI device */ + hdev = hci_alloc_dev_priv(sizeof_priv); + if (!hdev) { + BT_ERR("Can't allocate HCI device"); + err = -ENOMEM; + goto err_alloc; + } + + hu->hdev = hdev; + + hdev->bus = HCI_UART; + hci_set_drvdata(hdev, hu); + + INIT_WORK(&hu->init_ready, hci_uart_init_work); + INIT_WORK(&hu->write_work, hci_uart_write_work); + + /* Only when vendor specific setup callback is provided, consider + * the manufacturer information valid. This avoids filling in the + * value for Ericsson when nothing is specified. + */ + if (hu->proto->setup) + hdev->manufacturer = hu->proto->manufacturer; + + hdev->open = hci_uart_open; + hdev->close = hci_uart_close; + hdev->flush = hci_uart_flush; + hdev->send = hci_uart_send_frame; + hdev->setup = hci_uart_setup; + if (!hdev->wakeup) + hdev->wakeup = hci_uart_wakeup; + SET_HCIDEV_DEV(hdev, &hu->serdev->dev); + + if (test_bit(HCI_UART_NO_SUSPEND_NOTIFIER, &hu->flags)) + hci_set_quirk(hdev, HCI_QUIRK_NO_SUSPEND_NOTIFIER); + + if (test_bit(HCI_UART_RAW_DEVICE, &hu->hdev_flags)) + hci_set_quirk(hdev, HCI_QUIRK_RAW_DEVICE); + + if (test_bit(HCI_UART_EXT_CONFIG, &hu->hdev_flags)) + hci_set_quirk(hdev, HCI_QUIRK_EXTERNAL_CONFIG); + + if (test_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags)) + return 0; + + if (hci_register_dev(hdev) < 0) { + BT_ERR("Can't register HCI device"); + err = -ENODEV; + goto err_register; + } + + set_bit(HCI_UART_REGISTERED, &hu->flags); + + return 0; + +err_register: + hci_free_dev(hdev); +err_alloc: + clear_bit(HCI_UART_PROTO_READY, &hu->flags); + p->close(hu); +err_open: + serdev_device_close(hu->serdev); +err_rwsem: + percpu_free_rwsem(&hu->proto_lock); + return err; +} +EXPORT_SYMBOL_GPL(hci_uart_register_device_priv); + +void hci_uart_unregister_device(struct hci_uart *hu) +{ + struct hci_dev *hdev = hu->hdev; + + cancel_work_sync(&hu->init_ready); + if (test_bit(HCI_UART_REGISTERED, &hu->flags)) + hci_unregister_dev(hdev); + hci_free_dev(hdev); + + cancel_work_sync(&hu->write_work); + + hu->proto->close(hu); + + if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) { + clear_bit(HCI_UART_PROTO_READY, &hu->flags); + serdev_device_close(hu->serdev); + } + percpu_free_rwsem(&hu->proto_lock); +} +EXPORT_SYMBOL_GPL(hci_uart_unregister_device); -- cgit v1.3.1