CVE-2026-64238 in Linux
Summary
by MITRE • 07/24/2026
In the Linux kernel, the following vulnerability has been resolved:
gpio: shared: fix deadlock on shared proxy's parent removal
Commit 710abda58055 ("gpio: shared: call gpio_chip::of_xlate() if set") used the mutex embedded in struct gpio_shared_entry to protect the offset field which now can be modified after assignment. The critical section however is too wide and introduced a potential deadlock on the removal of the shared GPIO proxy's parent.
Make the critical section shorter - only protect the offset when it's being read.
While at it: mention the fact that the entry lock is now also used to protect against concurrent access to the offset field in the structure's documentation.
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Analysis
by VulDB Data Team • 07/24/2026
This vulnerability resides within the Linux kernel's GPIO subsystem, specifically addressing a deadlock condition that occurs during the removal of shared GPIO proxy parents. The issue stems from an overly broad critical section implementation that was introduced in commit 710abda58055, which modified how gpio_chip::of_xlate() is called within the shared GPIO framework. The original change attempted to protect the offset field within struct gpio_shared_entry using a mutex, but this approach created unintended consequences by expanding the scope of protection beyond what was necessary.
The technical flaw manifests when multiple threads attempt to access shared GPIO resources simultaneously, particularly during parent removal operations. The mutex embedded in struct gpio_shared_entry now protects the offset field, but this protection extends beyond just the offset modification itself. When a shared GPIO proxy's parent is being removed, the extended critical section creates a potential deadlock scenario where threads become blocked waiting for each other to release locks. This occurs because the same mutex that protects the offset field also guards other operations that may be required during parent removal, leading to circular wait conditions between different kernel subsystems.
The operational impact of this vulnerability is significant within embedded systems and device driver environments that rely heavily on GPIO sharing mechanisms. Systems utilizing shared GPIO resources may experience complete system hangs or unresponsive behavior when attempting to remove GPIO proxy parents, particularly in high-concurrency scenarios where multiple threads are simultaneously accessing GPIO resources. The deadlock condition affects not only the immediate GPIO subsystem but can propagate throughout the kernel, potentially causing broader system stability issues and requiring system reboot to resolve.
The mitigation strategy involves narrowing the critical section scope to protect only the offset field during actual read operations rather than maintaining protection throughout the entire access pattern. This approach aligns with best practices for lock granularity and reduces the likelihood of contention between different kernel subsystems. The fix ensures that the entry lock documented in the structure's comments now properly protects concurrent access to the offset field, addressing both the immediate deadlock issue and improving overall resource management efficiency. This vulnerability demonstrates the importance of careful lock design in kernel code, where overly broad protection can create more problems than it solves, and aligns with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and ATT&CK techniques related to system stability compromise through kernel-level resource contention.
The resolution maintains backward compatibility while improving the robustness of GPIO shared resource management. By restricting the mutex protection to only when the offset field is actually being read, the implementation reduces lock contention and eliminates the potential for deadlock conditions during parent removal operations. This change reflects proper kernel development practices where lock granularity is optimized to minimize performance impact while ensuring data integrity, particularly important in real-time embedded systems where predictable behavior is essential for system reliability.