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 --- net/bluetooth/hci_sysfs.c | 151 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 net/bluetooth/hci_sysfs.c (limited to 'net/bluetooth/hci_sysfs.c') diff --git a/net/bluetooth/hci_sysfs.c b/net/bluetooth/hci_sysfs.c new file mode 100644 index 000000000..c2065abf7 --- /dev/null +++ b/net/bluetooth/hci_sysfs.c @@ -0,0 +1,151 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Bluetooth HCI driver model support. */ + +#include + +#include +#include + +static const struct class bt_class = { + .name = "bluetooth", +}; + +static void bt_link_release(struct device *dev) +{ + struct hci_conn *conn = to_hci_conn(dev); + struct device *parent = dev->parent; + + kfree(conn); + put_device(parent); +} + +static const struct device_type bt_link = { + .name = "link", + .release = bt_link_release, +}; + +/* + * The rfcomm tty device will possibly retain even when conn + * is down, and sysfs doesn't support move zombie device, + * so we should move the device before conn device is destroyed. + */ +static int __match_tty(struct device *dev, const void *data) +{ + return !strncmp(dev_name(dev), "rfcomm", 6); +} + +void hci_conn_init_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + conn->dev.type = &bt_link; + conn->dev.class = &bt_class; + conn->dev.parent = get_device(&hdev->dev); + + device_initialize(&conn->dev); +} + +void hci_conn_add_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + if (device_is_registered(&conn->dev)) + return; + + dev_set_name(&conn->dev, "%s:%d", hdev->name, conn->handle); + + if (device_add(&conn->dev) < 0) + bt_dev_err(hdev, "failed to register connection device"); +} + +void hci_conn_del_sysfs(struct hci_conn *conn) +{ + struct hci_dev *hdev = conn->hdev; + + bt_dev_dbg(hdev, "conn %p", conn); + + if (!device_is_registered(&conn->dev)) { + /* If device_add() has *not* succeeded, use *only* put_device() + * to drop the reference count. + */ + put_device(&conn->dev); + return; + } + + /* If there are devices using the connection as parent reset it to NULL + * before unregistering the device. + */ + while (1) { + struct device *dev; + + dev = device_find_child(&conn->dev, NULL, __match_tty); + if (!dev) + break; + device_move(dev, NULL, DPM_ORDER_DEV_LAST); + put_device(dev); + } + + device_unregister(&conn->dev); +} + +static void bt_host_release(struct device *dev) +{ + struct hci_dev *hdev = to_hci_dev(dev); + + if (hci_dev_test_flag(hdev, HCI_UNREGISTER)) { + hci_release_dev(hdev); + } else { + cleanup_srcu_struct(&hdev->srcu); + kfree(hdev); + } + module_put(THIS_MODULE); +} + +static ssize_t reset_store(struct device *dev, struct device_attribute *attr, + const char *buf, size_t count) +{ + struct hci_dev *hdev = to_hci_dev(dev); + + if (hdev->reset) + hdev->reset(hdev); + + return count; +} +static DEVICE_ATTR_WO(reset); + +static struct attribute *bt_host_attrs[] = { + &dev_attr_reset.attr, + NULL, +}; +ATTRIBUTE_GROUPS(bt_host); + +static const struct device_type bt_host = { + .name = "host", + .release = bt_host_release, + .groups = bt_host_groups, +}; + +void hci_init_sysfs(struct hci_dev *hdev) +{ + struct device *dev = &hdev->dev; + + dev->type = &bt_host; + dev->class = &bt_class; + + __module_get(THIS_MODULE); + device_initialize(dev); +} + +int __init bt_sysfs_init(void) +{ + return class_register(&bt_class); +} + +void bt_sysfs_cleanup(void) +{ + class_unregister(&bt_class); +} -- cgit v1.3.1