CVE-2023-53508 in Linux
Summary
by MITRE • 10/01/2025
In the Linux kernel, the following vulnerability has been resolved:
ublk: fail to start device if queue setup is interrupted
In ublk_ctrl_start_dev(), if wait_for_completion_interruptible() is interrupted by signal, queues aren't setup successfully yet, so we have to fail UBLK_CMD_START_DEV, otherwise kernel oops can be triggered.
Reported by German when working on qemu-storage-deamon which requires single thread ublk daemon.
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Analysis
by VulDB Data Team • 01/23/2026
The vulnerability identified as CVE-2023-53508 affects the Linux kernel's unified block layer implementation known as ublk. This issue specifically manifests within the ublk_ctrl_start_dev() function where improper handling of interrupted queue setup operations can lead to system instability. The ublk subsystem provides a unified interface for block device drivers and is commonly utilized in virtualization environments, particularly with qemu-storage-daemon implementations that require single-threaded ublk daemon operations. The vulnerability arises from a race condition or improper error handling scenario that occurs during device initialization when signal interruptions occur during queue setup phases.
The technical flaw exists in the ublk driver's control plane implementation where the wait_for_completion_interruptible() function is used to manage queue setup synchronization. When a signal interrupts this waiting process, the function returns an interruptible status code, but the subsequent code path fails to properly validate whether queue setup completed successfully before proceeding. This oversight creates a scenario where the function attempts to complete the device start operation despite incomplete queue initialization, leading to potential kernel oops conditions. The issue is particularly critical because it can be triggered by external signals during the device initialization sequence, making it exploitable through process interruption techniques. According to CWE classification, this represents a weakness in error handling and resource management, specifically CWE-755, where improper handling of exceptional conditions leads to system instability.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the entire virtualization infrastructure. When a kernel oops occurs due to this condition, it can result in system panics or forced reboots, disrupting virtual machine operations and potentially causing data loss. The vulnerability is particularly concerning for environments using qemu-storage-daemon where single-threaded daemon operations are required, as the interruption scenarios that trigger this flaw are more likely to occur during the critical device setup phases. Attackers could potentially exploit this by sending signals to processes managing ublk devices, causing denial of service conditions that affect virtualized workloads. This vulnerability aligns with ATT&CK technique T1490, which involves manipulating system resources to cause denial of service conditions, and T1566, which covers initial access through exploitation of system vulnerabilities.
Mitigation strategies for CVE-2023-53508 should focus on implementing proper error handling and validation checks within the ublk subsystem. The most effective approach involves modifying the ublk_ctrl_start_dev() function to ensure that when wait_for_completion_interruptible() returns an interruptible status, the function properly fails the UBLK_CMD_START_DEV command and cleans up any partially initialized resources. System administrators should ensure their Linux kernel versions include the patched implementation that addresses this specific race condition. Additionally, monitoring for unusual signal activity during device initialization phases can help detect potential exploitation attempts. The fix should be applied across all systems running affected kernel versions, particularly those supporting virtualization environments where ublk drivers are actively used. Organizations utilizing qemu-storage-daemon implementations should prioritize patching to prevent potential denial of service scenarios that could impact their virtualized infrastructure.