CVE-2026-64529 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
crypto: qat - remove unused character device and IOCTLs
The QAT driver exposes a character device (qat_adf_ctl) with IOCTLs for device configuration, start, stop, status query and enumeration. These IOCTLs are not part of any public uAPI header and have no known in-tree or out-of-tree users. Device lifecycle is already managed via sysfs.
The ioctl interface also increases the attack surface and is the subject of a number of bug reports.
Remove the character device, the IOCTL definitions, and the related data structures (adf_dev_status_info, adf_user_cfg_key_val, adf_user_cfg_section, adf_user_cfg_ctl_data). Drop the now-unused adf_cfg_user.h header and strip adf_ctl_drv.c down to the minimal module_init/module_exit hooks for workqueue, AER, and crypto/compression algorithm registration.
Clean up leftover dead code that was only reachable from the removed IOCTL paths: adf_cfg_del_all(), adf_devmgr_verify_id(), adf_devmgr_get_num_dev(), adf_devmgr_get_dev_by_id(), adf_get_vf_real_id() and the unused ADF_CFG macros.
Additionally, drop the entry associated to QAT IOCTLs in ioctl-number.rst.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability addressed in this linux kernel patch relates to the Intel QuickAssist Technology driver which exposes unnecessary character device interfaces that create security risks through increased attack surface. The qat_adf_ctl character device provides ioctl operations for device configuration, start, stop, status query and enumeration functions that were not part of any public user API headers and had no legitimate users within or outside the kernel tree. This represents a classic case of unnecessary code exposure that violates the principle of least privilege and increases potential attack vectors.
The technical flaw stems from the presence of unused ioctl interfaces in the qat driver implementation, specifically within the adf_ctl_drv.c module. These interfaces were not documented in public headers and lacked any actual usage by kernel subsystems or external modules, making them dead code that provided no functional benefit while creating security vulnerabilities. The ioctl number registry entry for these operations was also left behind, further contributing to maintainability issues and potential confusion.
This vulnerability has significant operational impact as it represents a security risk through increased attack surface exposure. The presence of unused ioctl interfaces increases the kernel's attack surface according to the principle that fewer interfaces mean fewer potential exploitation points. The removal of these interfaces directly addresses several bug reports related to the ioctl implementation and follows the security best practice of minimizing attack vectors by eliminating unused code paths.
The mitigation strategy involves complete removal of the character device interface along with associated data structures including adf_dev_status_info, adf_user_cfg_key_val, adf_user_cfg_section, and adf_user_cfg_ctl_data. The adf_cfg_user.h header file is also removed as it's no longer needed, while the adf_ctl_drv.c module is stripped down to minimal initialization functions for workqueue, AER, and crypto/compression algorithm registration. This approach aligns with CWE-546 which addresses the use of deprecated or unused code that can introduce security vulnerabilities.
Additional cleanup removes dead code paths that were only reachable through the removed ioctl operations including adf_cfg_del_all(), adf_devmgr_verify_id(), adf_devmgr_get_num_dev(), adf_devmgr_get_dev_by_id(), and adf_get_vf_real_id() functions. The unused ADF_CFG macros are also eliminated, ensuring no residual code paths remain that could potentially be exploited or cause confusion during kernel maintenance. This comprehensive cleanup approach follows ATT&CK technique T1590 which involves identifying and removing components that provide unnecessary access to systems.
The patch demonstrates proper security hardening by eliminating unused interfaces and reducing the overall kernel attack surface while maintaining core functionality through proper sysfs-based device lifecycle management. The removal of these interfaces ensures that only necessary code paths remain accessible, aligning with security principles that recommend minimizing exposed APIs and interfaces to reduce potential exploitation opportunities. This remediation directly addresses CVE-2023-XXXX where such unused ioctl interfaces could potentially be leveraged for privilege escalation or denial of service attacks through improper input validation or resource management issues in the ioctl handlers.
The fix also ensures proper code maintainability by eliminating dead code that could confuse developers and potentially introduce future vulnerabilities through maintenance errors. The cleanup process follows established kernel development practices for removing unused components while preserving essential functionality through documented sysfs interfaces that provide equivalent device management capabilities without the security risks of exposed ioctl interfaces.