CVE-2026-72454 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
i3c: mipi-i3c-hci: Fix race in i3c_hci_addr_to_dev()
i3c_hci_addr_to_dev() walks bus->devs.i3c, which is protected by bus.lock (rwsem). However, it is invoked from the MIPI I3C HCI IRQ handler, which cannot take bus.lock. This allows concurrent device addition/removal in the I3C core to modify the list while it is being traversed, potentially leading to use-after-free or crashes.
Remove the dependency on the bus device list and introduce a dedicated lookup table. Add an ibi_devs[] array indexed by DAT entry, maintained
under hci->lock. Update the array when IBIs are enabled or disabled, so that it always reflects the set of devices allowed to generate IBIs. Also update when IBIs are freed, to cover the corner case when an IBI is freed without first being disabled (e.g. oldedev in i3c_master_add_i3c_dev_locked()).
Move i3c_hci_addr_to_dev() into core.c, reimplement it using the new array, and add a lockdep assertion to enforce that hci->lock is held by callers.
Demote a message in PIO and DMA IBI handling, from an error to a debug message, because there is a race window when the condition can arise normally.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability identified in the Linux kernel's i3c subsystem represents a critical race condition within the MIPI I3C HCI driver that could lead to system instability and potential security implications. This flaw exists in the i3c_hci_addr_to_dev() function which is responsible for mapping device addresses to their corresponding device structures within the I3C bus infrastructure. The core issue stems from improper synchronization mechanisms where the function accesses the bus device list without proper locking, creating a scenario where concurrent operations could corrupt data structures during traversal.
The technical flaw manifests when i3c_hci_addr_to_dev() traverses the bus->devs.i3c list that is protected by bus.lock which is an rwsem lock. However, this function is invoked from the MIPI I3C HCI IRQ handler context where acquiring bus.lock is not permissible due to potential deadlocks or system hangs. This architectural mismatch creates a dangerous race condition where device addition or removal operations in the I3C core can simultaneously modify the list structure while i3c_hci_addr_to_dev() is iterating through it, resulting in use-after-free conditions or kernel crashes that could be exploited by malicious actors.
This vulnerability directly maps to CWE-367 Time-of-Check Time-of-Use (TOCTOU) and CWE-129 Improper Validation of Array Index, as the system fails to properly validate device list integrity during concurrent access scenarios. The operational impact extends beyond simple system crashes to potentially enable privilege escalation attacks through controlled memory corruption, particularly when the I3C subsystem is actively managing device communications in embedded systems or IoT environments where kernel stability is paramount.
The mitigation strategy implemented involves restructuring the data access pattern by replacing the dependency on the bus device list with a dedicated lookup table mechanism. A new ibi_devs[] array indexed by DAT entry has been introduced and maintained under hci->lock protection, ensuring that all device lookups occur in a synchronized manner. This approach addresses the fundamental synchronization issue by creating a separate data structure that can be safely accessed without conflicting with the IRQ handler context requirements.
The solution also includes moving i3c_hci_addr_to_dev() implementation from its original location to core.c and adding lockdep assertions to enforce proper locking discipline, which aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation by preventing improper access patterns that could lead to kernel memory corruption. The array updates occur during IBIs enable/disable operations and when IBIs are freed, covering all possible corner cases including the specific scenario where i3c_master_add_i3c_dev_locked() processes older devices without proper disable sequences.
Additional improvements include demoting error messages in PIO and DMA IBI handling from error to debug levels, recognizing that certain race conditions can occur naturally during normal system operation rather than indicating actual failures. This change prevents log spamming while maintaining visibility into legitimate system behavior patterns that are inherent to the concurrent nature of interrupt-driven device management. The overall fix demonstrates a comprehensive approach to kernel security by addressing both the immediate race condition and its broader implications for system stability, following established best practices for concurrent data structure access in kernel space environments.