CVE-2025-38302 in Linux
Summary
by MITRE • 07/10/2025
In the Linux kernel, the following vulnerability has been resolved:
block: don't use submit_bio_noacct_nocheck in blk_zone_wplug_bio_work
Bios queued up in the zone write plug have already gone through all all preparation in the submit_bio path, including the freeze protection.
Submitting them through submit_bio_noacct_nocheck duplicates the work and can can cause deadlocks when freezing a queue with pending bio write plugs.
Go straight to ->submit_bio or blk_mq_submit_bio to bypass the superfluous extra freeze protection and checks.
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Analysis
by VulDB Data Team • 12/07/2025
The vulnerability identified as CVE-2025-38302 resides within the Linux kernel's block layer subsystem, specifically affecting how write plug operations are handled in zone management. This issue demonstrates a critical flaw in the kernel's I/O handling mechanism where redundant processing occurs during bio submission operations. The problem manifests when bios are queued in zone write plugs, which have already undergone complete preparation through the standard submit_bio path including freeze protection mechanisms. The implementation error causes these already-prepared bios to be processed through an alternative submission path that duplicates existing work and introduces potential deadlock conditions. This vulnerability represents a fundamental design flaw in the kernel's bio submission pipeline where unnecessary code paths are executed, creating operational instability in storage subsystems that utilize zone-based storage technologies.
The technical root cause of this vulnerability stems from the inappropriate use of submit_bio_noacct_nocheck within the blk_zone_wplug_bio_work function. This function processes bios that are already prepared through the standard submit_bio path, which includes essential freeze protection mechanisms designed to prevent concurrent access issues during queue freezing operations. When the code attempts to submit these pre-prepared bios through submit_bio_noacct_nocheck, it essentially performs duplicate operations including redundant freeze protection checks and accounting operations. This duplication creates a scenario where the same resources are protected multiple times, leading to potential deadlock conditions when attempting to freeze a queue that contains pending bio write plugs. The flaw violates fundamental kernel design principles by introducing redundant processing that was not intended to be executed, as the bios have already been through the complete preparation phase.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially catastrophic system instability. When the kernel attempts to freeze a queue containing pending bio write plugs, the duplicate freeze protection mechanisms can cause circular dependencies and resource contention that result in system deadlocks. This scenario is particularly dangerous in storage environments where zone management is critical for maintaining data integrity and preventing race conditions. The vulnerability affects systems utilizing zone-based storage technologies such as ZNS (Zoned Name Space) SSDs where write plugs are commonly used to optimize I/O operations. The deadlock conditions can lead to complete system hangs where no further I/O operations can proceed, requiring manual intervention or system reboot to restore functionality. This represents a significant threat to system availability in production environments where continuous I/O operations are expected.
The mitigation strategy for this vulnerability involves modifying the blk_zone_wplug_bio_work function to bypass the unnecessary submit_bio_noacct_nocheck path and instead directly invoke either the standard ->submit_bio or blk_mq_submit_bio functions. This approach eliminates the redundant freeze protection checks and accounting operations that cause the duplication issue. The fix aligns with established kernel development practices where redundant code paths are removed to prevent operational instability. This solution addresses the core problem by ensuring that bios that have already been prepared through the complete submit_bio path are not unnecessarily reprocessed through alternative submission mechanisms. The implementation follows standard kernel security practices for preventing deadlocks and race conditions, and it maintains the integrity of the existing freeze protection mechanisms while eliminating the problematic duplication. This remediation approach is consistent with the principle of least privilege and minimal change, ensuring that only the necessary modifications are made to resolve the vulnerability without disrupting other kernel functionality. The fix directly addresses the CWE-121 memory safety issue category and aligns with ATT&CK techniques related to system resource exhaustion and denial of service conditions.