CVE-2025-71200 Overview
A vulnerability has been identified in the Linux kernel's MMC (MultiMediaCard) subsystem, specifically within the sdhci-of-dwcmshc driver used for Rockchip DWC MSHC controllers. The vulnerability allows illegal clock frequency reduction when operating in HS200 or HS400 timing modes, which can lead to link failure and system instability.
When operating in HS200 or HS400 timing modes, reducing the clock frequency below 52MHz causes the communication link to break, as the Rockchip DWC MSHC controller requires maintaining a minimum clock of 52MHz in these high-speed modes. This can be triggered through the debugfs interface, leading to CQE (Command Queue Engine) recovery failures and potential system warnings.
Critical Impact
Exploitation of this vulnerability can cause MMC link failures, CQE recovery errors, and kernel warnings that may impact system stability on devices using Rockchip DWC MSHC controllers.
Affected Products
- Linux kernel with sdhci-of-dwcmshc driver
- Systems using Rockchip RK3588 and similar SoCs with DWC MSHC controllers
- Devices operating MMC in HS200 or HS400 timing modes
Discovery Timeline
- 2026-02-14 - CVE CVE-2025-71200 published to NVD
- 2026-02-18 - Last updated in NVD database
Technical Details for CVE-2025-71200
Vulnerability Analysis
The vulnerability exists in the sdhci-of-dwcmshc driver, which handles the Synopsis DesignWare Mobile Storage Host Controller interface for platforms like Rockchip. The driver failed to implement proper validation of clock frequency changes when the MMC interface is operating in high-speed modes (HS200 or HS400).
The HS200 and HS400 timing modes are high-performance operating modes for eMMC storage that require strict adherence to timing specifications. The Rockchip DWC MSHC controller specifically requires a minimum clock frequency of 52MHz when operating in these modes. Prior to the fix, the driver allowed clock frequency changes through the debugfs interface without validating whether the new frequency met the minimum requirements for the current timing mode.
Root Cause
The root cause is the lack of input validation in the clock configuration path of the sdhci-of-dwcmshc driver. The driver's debugfs interface allowed arbitrary clock frequency values to be written to /sys/kernel/debug/mmc0/clock without checking if the requested frequency was compatible with the current timing mode. When a frequency below 52MHz was set while operating in HS200/HS400 mode, it violated the hardware requirements, causing the communication link to fail.
Attack Vector
The attack vector requires local access to the system with sufficient privileges to write to the debugfs interface. An attacker with root access or appropriate capabilities could trigger this vulnerability by writing an invalid clock value through the debugfs filesystem.
The vulnerability manifests when a clock frequency below 52MHz is written to the debugfs clock interface while the MMC controller is operating in HS200 or HS400 mode. This causes the hardware link to break, triggering CQE recovery procedures that subsequently fail, resulting in kernel warnings and potential system instability.
As shown in the kernel logs from the CVE description, when the clock is set to 50000000 (50MHz) via echo 50000000 > /sys/kernel/debug/mmc0/clock, the system experiences CQE recovery failures, halt failures, and spurious TCN (Task Completion Notification) events, ultimately resulting in a kernel WARNING.
Detection Methods for CVE-2025-71200
Indicators of Compromise
- Kernel log messages indicating mmc0: running CQE recovery followed by mmc0: cqhci: Failed to halt
- WARNING messages originating from drivers/mmc/host/cqhci-core.c at the cqhci_irq function
- Spurious TCN (Task Completion Notification) messages for MMC tags
- System instability or storage access failures on Rockchip-based platforms
Detection Strategies
- Monitor kernel logs (dmesg, /var/log/kern.log) for CQE recovery and halt failure messages from the cqhci subsystem
- Implement auditd rules to track writes to /sys/kernel/debug/mmc*/clock debugfs interfaces
- Monitor for unusual patterns of MMC subsystem errors that may indicate exploitation attempts
- Check for unauthorized access to debugfs mount points on production systems
Monitoring Recommendations
- Configure centralized logging to capture kernel warnings and MMC subsystem errors
- Implement file integrity monitoring on debugfs access patterns
- Set up alerts for repeated CQE recovery failures in the MMC subsystem
- Monitor system stability metrics on devices using Rockchip DWC MSHC controllers
How to Mitigate CVE-2025-71200
Immediate Actions Required
- Update to a patched Linux kernel version that includes the clock validation fix
- Restrict access to the debugfs filesystem on production systems
- Limit root access and capabilities that allow debugfs writes
- Consider unmounting or disabling debugfs on production systems where it's not required
Patch Information
The vulnerability has been addressed through multiple kernel commits that add validation to prevent illegal clock reduction in HS200/HS400 modes. The fix adds a check to ensure clock frequencies below 52MHz are rejected when the controller is operating in these high-speed timing modes.
Patches are available from the following kernel git commits:
- Kernel Git Commit 3009738a855c
- Kernel Git Commit 36be050f21de
- Kernel Git Commit 59b8a1ca6df4
- Kernel Git Commit de0ad7156036
- Kernel Git Commit f2677d6e2bbc
Workarounds
- Unmount or restrict access to debugfs on production systems where clock manipulation is not needed
- Implement strict access controls limiting root access on affected systems
- Use SELinux or AppArmor policies to restrict writes to MMC debugfs interfaces
- Monitor and alert on any attempts to modify MMC clock settings through debugfs
# Configuration example - Restrict debugfs access
# Unmount debugfs on production systems
umount /sys/kernel/debug
# Or restrict access via permissions (if debugfs must remain mounted)
chmod 700 /sys/kernel/debug
chmod 700 /sys/kernel/debug/mmc*
# Example SELinux policy to deny writes to mmc debugfs
# semodule -i mmc_debugfs_deny.pp
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
