CVE-2026-63885

In the Linux kernel, the following vulnerability has been resolved:

drm/gem: fix race between change_handle and handle_delete

drm_gem_change_handle_ioctl leaves the old handle live in the IDR during the window between spin_unlock(table_lock) and the final spin_lock(table_lock). A concurrent drm_gem_handle_delete on the old handle succeeds in this window, decrements handle_count to 0, and frees the GEM object while the new handles IDR entry still references it.

NULL the old handles IDR entry before dropping table_lock so that any concurrent GEM_CLOSE on the old handle sees NULL and returns -EINVAL. Restore the old entry on the prime-bookkeeping error path.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/0dfa42cfe4dbe114533480503934f43e33c1e83d
• https://git.kernel.org/stable/c/7164d78559b0ff29931a366a840a9e5dd53d4b7c
• https://git.kernel.org/stable/c/cde2c9257cbe8463b9dcf7b1075177b72b5fd938