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/eir.c | 389 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 389 insertions(+) create mode 100644 net/bluetooth/eir.c (limited to 'net/bluetooth/eir.c') diff --git a/net/bluetooth/eir.c b/net/bluetooth/eir.c new file mode 100644 index 000000000..a55696820 --- /dev/null +++ b/net/bluetooth/eir.c @@ -0,0 +1,389 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * BlueZ - Bluetooth protocol stack for Linux + * + * Copyright (C) 2021 Intel Corporation + */ + +#include +#include +#include + +#include "eir.h" + +#define PNP_INFO_SVCLASS_ID 0x1200 + +u8 eir_append_local_name(struct hci_dev *hdev, u8 *ptr, u8 ad_len) +{ + size_t short_len; + size_t complete_len; + + /* no space left for name (+ type + len) */ + if ((max_adv_len(hdev) - ad_len) < HCI_MAX_SHORT_NAME_LENGTH + 2) + return ad_len; + + /* use complete name if present and fits */ + complete_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name)); + if (complete_len && complete_len <= HCI_MAX_SHORT_NAME_LENGTH) + return eir_append_data(ptr, ad_len, EIR_NAME_COMPLETE, + hdev->dev_name, complete_len); + + /* use short name if present */ + short_len = strnlen(hdev->short_name, sizeof(hdev->short_name)); + if (short_len) + return eir_append_data(ptr, ad_len, EIR_NAME_SHORT, + hdev->short_name, + short_len); + + /* use shortened full name if present, we already know that name + * is longer then HCI_MAX_SHORT_NAME_LENGTH + */ + if (complete_len) + return eir_append_data(ptr, ad_len, EIR_NAME_SHORT, + hdev->dev_name, + HCI_MAX_SHORT_NAME_LENGTH); + + return ad_len; +} + +u8 eir_append_appearance(struct hci_dev *hdev, u8 *ptr, u8 ad_len) +{ + return eir_append_le16(ptr, ad_len, EIR_APPEARANCE, hdev->appearance); +} + +u8 eir_append_service_data(u8 *eir, u16 eir_len, u16 uuid, u8 *data, + u8 data_len) +{ + eir[eir_len++] = sizeof(u8) + sizeof(uuid) + data_len; + eir[eir_len++] = EIR_SERVICE_DATA; + put_unaligned_le16(uuid, &eir[eir_len]); + eir_len += sizeof(uuid); + memcpy(&eir[eir_len], data, data_len); + eir_len += data_len; + + return eir_len; +} + +static u8 *create_uuid16_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len) +{ + u8 *ptr = data, *uuids_start = NULL; + struct bt_uuid *uuid; + + if (len < 4) + return ptr; + + list_for_each_entry(uuid, &hdev->uuids, list) { + u16 uuid16; + + if (uuid->size != 16) + continue; + + uuid16 = get_unaligned_le16(&uuid->uuid[12]); + if (uuid16 < 0x1100) + continue; + + if (uuid16 == PNP_INFO_SVCLASS_ID) + continue; + + if (!uuids_start) { + uuids_start = ptr; + uuids_start[0] = 1; + uuids_start[1] = EIR_UUID16_ALL; + ptr += 2; + } + + /* Stop if not enough space to put next UUID */ + if ((ptr - data) + sizeof(u16) > len) { + uuids_start[1] = EIR_UUID16_SOME; + break; + } + + *ptr++ = (uuid16 & 0x00ff); + *ptr++ = (uuid16 & 0xff00) >> 8; + uuids_start[0] += sizeof(uuid16); + } + + return ptr; +} + +static u8 *create_uuid32_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len) +{ + u8 *ptr = data, *uuids_start = NULL; + struct bt_uuid *uuid; + + if (len < 6) + return ptr; + + list_for_each_entry(uuid, &hdev->uuids, list) { + if (uuid->size != 32) + continue; + + if (!uuids_start) { + uuids_start = ptr; + uuids_start[0] = 1; + uuids_start[1] = EIR_UUID32_ALL; + ptr += 2; + } + + /* Stop if not enough space to put next UUID */ + if ((ptr - data) + sizeof(u32) > len) { + uuids_start[1] = EIR_UUID32_SOME; + break; + } + + memcpy(ptr, &uuid->uuid[12], sizeof(u32)); + ptr += sizeof(u32); + uuids_start[0] += sizeof(u32); + } + + return ptr; +} + +static u8 *create_uuid128_list(struct hci_dev *hdev, u8 *data, ptrdiff_t len) +{ + u8 *ptr = data, *uuids_start = NULL; + struct bt_uuid *uuid; + + if (len < 18) + return ptr; + + list_for_each_entry(uuid, &hdev->uuids, list) { + if (uuid->size != 128) + continue; + + if (!uuids_start) { + uuids_start = ptr; + uuids_start[0] = 1; + uuids_start[1] = EIR_UUID128_ALL; + ptr += 2; + } + + /* Stop if not enough space to put next UUID */ + if ((ptr - data) + 16 > len) { + uuids_start[1] = EIR_UUID128_SOME; + break; + } + + memcpy(ptr, uuid->uuid, 16); + ptr += 16; + uuids_start[0] += 16; + } + + return ptr; +} + +void eir_create(struct hci_dev *hdev, u8 *data) +{ + u8 *ptr = data; + size_t name_len; + + name_len = strnlen(hdev->dev_name, sizeof(hdev->dev_name)); + + if (name_len > 0) { + /* EIR Data type */ + if (name_len > 48) { + name_len = 48; + ptr[1] = EIR_NAME_SHORT; + } else { + ptr[1] = EIR_NAME_COMPLETE; + } + + /* EIR Data length */ + ptr[0] = name_len + 1; + + memcpy(ptr + 2, hdev->dev_name, name_len); + + ptr += (name_len + 2); + } + + if (hdev->inq_tx_power != HCI_TX_POWER_INVALID) { + ptr[0] = 2; + ptr[1] = EIR_TX_POWER; + ptr[2] = (u8)hdev->inq_tx_power; + + ptr += 3; + } + + if (hdev->devid_source > 0) { + ptr[0] = 9; + ptr[1] = EIR_DEVICE_ID; + + put_unaligned_le16(hdev->devid_source, ptr + 2); + put_unaligned_le16(hdev->devid_vendor, ptr + 4); + put_unaligned_le16(hdev->devid_product, ptr + 6); + put_unaligned_le16(hdev->devid_version, ptr + 8); + + ptr += 10; + } + + ptr = create_uuid16_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data)); + ptr = create_uuid32_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data)); + ptr = create_uuid128_list(hdev, ptr, HCI_MAX_EIR_LENGTH - (ptr - data)); +} + +u8 eir_create_per_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr) +{ + struct adv_info *adv = NULL; + u8 ad_len = 0; + + /* Return 0 when the current instance identifier is invalid. */ + if (instance) { + adv = hci_find_adv_instance(hdev, instance); + if (!adv) + return 0; + } + + if (adv) { + memcpy(ptr, adv->per_adv_data, adv->per_adv_data_len); + ad_len += adv->per_adv_data_len; + ptr += adv->per_adv_data_len; + } + + return ad_len; +} + +u8 eir_create_adv_data(struct hci_dev *hdev, u8 instance, u8 *ptr, u8 size) +{ + struct adv_info *adv = NULL; + u8 ad_len = 0, flags = 0; + u32 instance_flags; + + /* Return 0 when the current instance identifier is invalid. */ + if (instance) { + adv = hci_find_adv_instance(hdev, instance); + if (!adv) + return 0; + } + + instance_flags = hci_adv_instance_flags(hdev, instance); + + /* If instance already has the flags set skip adding it once + * again. + */ + if (adv && eir_get_data(adv->adv_data, adv->adv_data_len, EIR_FLAGS, + NULL)) + goto skip_flags; + + /* The Add Advertising command allows userspace to set both the general + * and limited discoverable flags. + */ + if (instance_flags & MGMT_ADV_FLAG_DISCOV) + flags |= LE_AD_GENERAL; + + if (instance_flags & MGMT_ADV_FLAG_LIMITED_DISCOV) + flags |= LE_AD_LIMITED; + + if (!hci_dev_test_flag(hdev, HCI_BREDR_ENABLED)) + flags |= LE_AD_NO_BREDR; + + if (flags || (instance_flags & MGMT_ADV_FLAG_MANAGED_FLAGS)) { + /* If a discovery flag wasn't provided, simply use the global + * settings. + */ + if (!flags) + flags |= mgmt_get_adv_discov_flags(hdev); + + /* Only add the "Flags" if it fits together with the instance + * advertising data; drop it rather than overflow the buffer. + */ + if (flags && + (ad_len + eir_precalc_len(1) + + (adv ? adv->adv_data_len : 0) <= size)) { + ptr[0] = 0x02; + ptr[1] = EIR_FLAGS; + ptr[2] = flags; + + ad_len += 3; + ptr += 3; + } + } + +skip_flags: + if (adv) { + memcpy(ptr, adv->adv_data, adv->adv_data_len); + ad_len += adv->adv_data_len; + ptr += adv->adv_data_len; + } + + if (instance_flags & MGMT_ADV_FLAG_TX_POWER) { + s8 adv_tx_power; + + if (ext_adv_capable(hdev)) { + if (adv) + adv_tx_power = adv->tx_power; + else + adv_tx_power = hdev->adv_tx_power; + } else { + adv_tx_power = hdev->adv_tx_power; + } + + /* Provide Tx Power only if we can provide a valid value for it */ + if (adv_tx_power != HCI_TX_POWER_INVALID && + (ad_len + eir_precalc_len(1) <= size)) { + ptr[0] = 0x02; + ptr[1] = EIR_TX_POWER; + ptr[2] = (u8)adv_tx_power; + + ad_len += 3; + ptr += 3; + } + } + + return ad_len; +} + +static u8 create_default_scan_rsp(struct hci_dev *hdev, u8 *ptr) +{ + u8 scan_rsp_len = 0; + + if (hdev->appearance) + scan_rsp_len = eir_append_appearance(hdev, ptr, scan_rsp_len); + + return eir_append_local_name(hdev, ptr, scan_rsp_len); +} + +u8 eir_create_scan_rsp(struct hci_dev *hdev, u8 instance, u8 *ptr) +{ + struct adv_info *adv; + u8 scan_rsp_len = 0; + + if (!instance) + return create_default_scan_rsp(hdev, ptr); + + adv = hci_find_adv_instance(hdev, instance); + if (!adv) + return 0; + + if ((adv->flags & MGMT_ADV_FLAG_APPEARANCE) && hdev->appearance) + scan_rsp_len = eir_append_appearance(hdev, ptr, scan_rsp_len); + + memcpy(&ptr[scan_rsp_len], adv->scan_rsp_data, adv->scan_rsp_len); + + scan_rsp_len += adv->scan_rsp_len; + + if (adv->flags & MGMT_ADV_FLAG_LOCAL_NAME) + scan_rsp_len = eir_append_local_name(hdev, ptr, scan_rsp_len); + + return scan_rsp_len; +} + +void *eir_get_service_data(u8 *eir, size_t eir_len, u16 uuid, size_t *len) +{ + const u8 *eir_end = eir + eir_len; + size_t dlen; + + while ((eir = eir_get_data(eir, eir_len, EIR_SERVICE_DATA, &dlen))) { + u16 value = get_unaligned_le16(eir); + + if (uuid == value) { + if (len) + *len = dlen - 2; + return &eir[2]; + } + + eir += dlen; + eir_len = eir_end - eir; + } + + return NULL; +} -- cgit v1.3.1