CVE-2026-74306 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
vfio/qat: fix f_pos race in qat_vf_resume_write()
qat_vf_resume_write() checks filp->f_pos before taking migf->lock, but copies into the migration-state buffer after taking the lock and re-reading the shared file position.
Two concurrent writers could therefore pass the bounds check with the old offset, then have the second writer copy after the first advanced f_pos, writing past the end of the migration-state buffer.
Take migf->lock before doing the boundary checks.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides in the Linux kernel's VFIO QuickAssist Technology driver implementation where a race condition exists in the qat_vf_resume_write() function. This flaw manifests as a classic data race scenario involving file position tracking and concurrent access to shared memory buffers. The issue stems from improper locking sequence during migration state buffer operations, creating a window where multiple concurrent writers can corrupt memory boundaries.
The technical implementation flaw occurs when the function performs bounds checking against filp->f_pos before acquiring migf->lock, yet copies data into the migration-state buffer only after obtaining the lock and re-reading the file position. This ordering creates a temporal gap where two simultaneous writers might both pass initial boundary checks using an outdated file position value. When the first writer advances f_pos and the second writer executes its copy operation, the second writer effectively writes beyond the allocated buffer boundaries, resulting in potential memory corruption.
This vulnerability directly relates to CWE-367 Time-of-Check to Time-of-Use (TOCTOU) weakness, where the system state changes between the validation phase and the actual operation. The race condition scenario aligns with ATT&CK technique T1059.001 Command and Scripting Interpreter: PowerShell, though more specifically represents a kernel-level memory corruption vulnerability that could enable privilege escalation or system instability. The flaw operates at the kernel level where concurrent access to shared resources without proper synchronization mechanisms creates exploitable conditions.
The operational impact of this vulnerability extends beyond simple data corruption, potentially enabling attackers to manipulate migration state information and compromise the integrity of QuickAssist Technology operations. Under high-concurrency workloads involving VFIO device management, this race condition could lead to system crashes, data loss, or more severe security implications if exploited through malicious device drivers or kernel exploits. The vulnerability affects systems utilizing QAT hardware acceleration with VFIO virtualization capabilities.
Mitigation strategies should prioritize the immediate implementation of proper locking ordering where migf->lock is acquired before performing any boundary checks against filp->f_pos. This ensures atomic access to both the file position and buffer operations, eliminating the race window entirely. Additionally, implementing proper kernel memory bounds checking mechanisms and enhancing concurrent access controls for VFIO device migration operations would provide comprehensive protection. System administrators should ensure timely kernel updates addressing this specific vulnerability while monitoring for potential exploitation attempts through abnormal device driver behavior or system stability issues related to QAT hardware acceleration components.