CVE-2022-50314 in Linux
Summary
by MITRE • 09/15/2025
In the Linux kernel, the following vulnerability has been resolved:
nbd: Fix hung when signal interrupts nbd_start_device_ioctl()
syzbot reported hung task [1]. The following program is a simplified
version of the reproducer:
int main(void) {
int sv[2], fd;
if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) < 0) return 1; if ((fd = open("/dev/nbd0", 0)) < 0) return 1; if (ioctl(fd, NBD_SET_SIZE_BLOCKS, 0x81) < 0) return 1; if (ioctl(fd, NBD_SET_SOCK, sv[0]) < 0)
return 1; if (ioctl(fd, NBD_DO_IT) < 0) return 1; return 0; }
When signal interrupt nbd_start_device_ioctl() waiting the condition atomic_read(&config->recv_threads) == 0, the task can hung because it waits the completion of the inflight IOs.
This patch fixes the issue by clearing queue, not just shutdown, when signal interrupt nbd_start_device_ioctl().
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Analysis
by VulDB Data Team • 01/10/2026
The vulnerability CVE-2022-50314 affects the Linux kernel's network block device implementation, specifically within the nbd_start_device_ioctl() function. This issue represents a classic race condition and improper signal handling scenario that can lead to system hang conditions. The vulnerability manifests when a signal interrupts the ioctl operation while waiting for a specific condition related to network block device threads. The technical flaw occurs in the synchronization mechanism where the kernel fails to properly handle signal interruptions during the device configuration process, creating a deadlock scenario.
The root cause lies in how the kernel handles the shutdown sequence when a signal interrupts the nbd_start_device_ioctl() function. When the system waits for atomic_read(&config->recv_threads) == 0 to complete, a signal interrupt can cause the task to hang indefinitely because the kernel only performs shutdown operations rather than clearing the queue. This behavior creates a scenario where inflight I/O operations remain in an inconsistent state, preventing proper task completion and system recovery. The vulnerability is classified under CWE-667, which addresses improper lock handling, and specifically relates to improper synchronization in concurrent programming contexts.
The operational impact of this vulnerability extends beyond simple system hang conditions to potentially affect system stability and availability. When triggered, the affected system can become unresponsive to further nbd operations, requiring manual intervention or system reboot to restore normal functionality. This vulnerability is particularly concerning in environments where network block devices are actively used for storage operations, as it can lead to denial of service conditions that impact critical applications relying on distributed storage. The issue can be exploited by unprivileged users who have access to the nbd device, making it a significant security concern.
The fix implemented addresses the core synchronization problem by modifying the shutdown behavior to include queue clearing operations instead of merely shutting down the device. This change ensures that when a signal interrupts the ioctl operation, all pending I/O operations are properly cleared from the queue rather than being left in a hung state. The solution aligns with ATT&CK technique T1499.004, which covers the use of system shutdown/reboot to disrupt services, though in this case the disruption is accidental rather than malicious. The patch resolves the issue by ensuring proper cleanup of inflight operations during signal interruption scenarios, preventing the indefinite wait condition that previously occurred. This fix demonstrates proper handling of asynchronous operations and signal interruption in kernel space, following best practices for concurrent programming and resource management in operating system kernels.