CVE-2026-68101 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu: fix check in amdgpu_hmm_invalidate_gfx
For a short moment during alloc/free the userptr BO is not part of his VM, so bo->vm_bo can be NULL.
Keep a reference to the VM root PD as parent of the userptr BO so that we can always use that to wait for all submissions of the VM instead of only the one involving the userptr BO.
(cherry picked from commit 631849ff5d603841e74f19f4a5e30fe1f7d7cf30)
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in question affects the amdgpu driver within the Linux kernel, specifically addressing a race condition during memory management operations involving userptr buffer objects. This issue occurs in the drm/amdgpu subsystem where the graphics driver handles memory allocation and deallocation for user-space applications. The flaw manifests when a userptr buffer object is being processed during its allocation or deallocation phase, creating a temporary window where the buffer object is not properly associated with its virtual memory context.
The core technical issue stems from a null pointer dereference scenario where bo->vm_bo can become NULL during the brief period between allocation and full initialization of the buffer object within its virtual memory space. This condition creates an inconsistent state where the driver cannot reliably determine the proper virtual memory context for the buffer object, potentially leading to improper memory management operations. The vulnerability is classified as a race condition that violates proper synchronization principles in kernel memory management.
The operational impact of this vulnerability could result in system instability, potential crashes, or memory corruption when applications perform graphics operations involving userptr buffer objects. Such issues typically manifest during high-frequency allocation/deallocation patterns or concurrent memory access scenarios where the timing window for the null pointer condition is exploited. The vulnerability affects graphics processing units utilizing AMDGPU drivers and could potentially be leveraged to cause denial of service conditions or in rare cases, privilege escalation scenarios.
The fix implemented addresses this by maintaining a reference to the VM root page directory as the parent of the userptr buffer object, ensuring that all memory submissions can be properly tracked and synchronized regardless of whether the buffer object is currently associated with its virtual memory context. This approach aligns with established best practices for kernel memory management and follows principles outlined in common weakness enumeration standards such as CWE-362 for race conditions and CWE-476 for null pointer dereferences. The solution also demonstrates adherence to ATT&CK framework concepts related to privilege escalation and defense evasion through proper memory management techniques.
The cherry-picked commit from the mainline kernel repository indicates this is a well-tested and validated fix that has been integrated into stable kernel releases, reflecting industry-standard practices for vulnerability remediation in operating system components. This type of fix typically requires careful consideration of memory ordering constraints and synchronization primitives to ensure that all submitted operations are properly synchronized before memory cleanup occurs, preventing the race condition that could lead to system instability or data corruption during graphics processing operations involving userptr buffer objects.