CVE-2022-48878 in Linux
Summary
by MITRE • 08/21/2024
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_qca: Fix driver shutdown on closed serdev
The driver shutdown callback (which sends EDL_SOC_RESET to the device over serdev) should not be invoked when HCI device is not open (e.g. if hci_dev_open_sync() failed), because the serdev and its TTY are not open either. Also skip this step if device is powered off (qca_power_shutdown()).
The shutdown callback causes use-after-free during system reboot with Qualcomm Atheros Bluetooth:
Unable to handle kernel paging request at virtual address 0072662f67726fd7 ... CPU: 6 PID: 1 Comm: systemd-shutdow Tainted: G W 6.1.0-rt5-00325-g8a5f56bcfcca #8 Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT) Call trace: tty_driver_flush_buffer+0x4/0x30 serdev_device_write_flush+0x24/0x34 qca_serdev_shutdown+0x80/0x130 [hci_uart]
device_shutdown+0x15c/0x260 kernel_restart+0x48/0xac
KASAN report:
BUG: KASAN: use-after-free in tty_driver_flush_buffer+0x1c/0x50 Read of size 8 at addr ffff16270c2e0018 by task systemd-shutdow/1
CPU: 7 PID: 1 Comm: systemd-shutdow Not tainted 6.1.0-next-20221220-00014-gb85aaf97fb01-dirty #28 Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT) Call trace: dump_backtrace.part.0+0xdc/0xf0 show_stack+0x18/0x30 dump_stack_lvl+0x68/0x84 print_report+0x188/0x488 kasan_report+0xa4/0xf0 __asan_load8+0x80/0xac tty_driver_flush_buffer+0x1c/0x50 ttyport_write_flush+0x34/0x44 serdev_device_write_flush+0x48/0x60 qca_serdev_shutdown+0x124/0x274 device_shutdown+0x1e8/0x350 kernel_restart+0x48/0xb0 __do_sys_reboot+0x244/0x2d0 __arm64_sys_reboot+0x54/0x70 invoke_syscall+0x60/0x190 el0_svc_common.constprop.0+0x7c/0x160 do_el0_svc+0x44/0xf0 el0_svc+0x2c/0x6c el0t_64_sync_handler+0xbc/0x140 el0t_64_sync+0x190/0x194
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Analysis
by VulDB Data Team • 02/17/2026
The vulnerability described in CVE-2022-48878 affects the Linux kernel's Bluetooth subsystem, specifically within the Qualcomm Atheros Bluetooth driver implementation. This issue manifests during system shutdown when the HCI (Host Controller Interface) device shutdown callback attempts to execute operations on a closed serial device, leading to a use-after-free condition that can cause system instability and potential crashes. The flaw occurs in the hci_qca driver module which handles Qualcomm Atheros Bluetooth hardware, particularly affecting systems using the qca_power_shutdown mechanism for device power management.
The technical root cause stems from improper state validation within the driver shutdown sequence where the qca_serdev_shutdown function attempts to communicate with the Bluetooth device using serdev operations even when the underlying serial device is not properly initialized or has already been closed. This situation typically arises when hci_dev_open_sync() fails during the device initialization process, leaving the serdev and its associated TTY interface in a closed state. The kernel's KASAN (Kernel Address Sanitizer) reports indicate that the system attempts to access freed memory locations during the tty_driver_flush_buffer operation, which is triggered by the shutdown sequence attempting to flush pending writes to a closed device.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise system integrity during critical shutdown operations. When the system attempts to reboot or shutdown, the improper shutdown callback execution causes memory corruption that manifests as kernel paging faults and use-after-free errors. The specific error patterns show that the system attempts to access virtual address 0072662f67726fd7 and encounters memory at location ffff16270c2e0018 which has already been freed, indicating a classic use-after-free scenario that violates memory safety principles. This vulnerability particularly affects embedded systems using Qualcomm Technologies Inc. Robotics RB5 platforms running kernel versions 6.1.0-rt5 and later.
Mitigation strategies for this vulnerability involve implementing proper state checks within the driver shutdown callback to ensure that serdev operations only occur when the underlying device is properly initialized and open. The fix requires modifications to the qca_serdev_shutdown function to verify that the HCI device is both open and powered on before attempting any communication with the Bluetooth device. This approach aligns with CWE-416 (Use After Free) remediation guidelines and follows ATT&CK technique T1547.001 (Registry Run Keys/Startup Folder) by ensuring proper device state management during system operations. Additionally, system administrators should ensure that kernel updates containing the patched driver code are applied, particularly on embedded platforms where such shutdown scenarios are more frequent. The vulnerability demonstrates the importance of proper resource lifecycle management in kernel drivers and highlights the need for comprehensive testing of shutdown sequences in embedded Bluetooth implementations.