CVE-2026-98144 in Linux
Summary
by MITRE • 09/25/2026
In the Linux kernel, the following vulnerability has been resolved:
accel/amdxdna: put the chained BO when its mapping fails
amdxdna_cmd_set_error() looks up the first BO of a command chain, which takes a reference, and drops it at the end of the function. The mapping of that BO is established in between, and the failure path returns without the put, so the reference is leaked.
Ordinary use does not reach it. The chain has been submitted before any of this runs, so aie2_cmdlist_fill_slot() has already called amdxdna_cmd_get_op() on that BO and amdxdna_gem_vmap() has cached its address. What makes it reachable is that the BO is resolved again by handle here, and the handle is userspace's to recycle: closing it after submission and importing a dma-buf whose exporter implements no vmap onto the same id leaves amdxdna_gem_get_obj() returning an object this cannot map, since prime_import() types every import AMDXDNA_BO_SHARE.
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Analysis
by VulDB Data Team • 09/25/2026
The vulnerability identified in the Linux kernel's acceleration driver for AMD XDNA devices represents a reference counting error that leads to memory leaks under specific edge cases involving buffer object management and user-space handle recycling. The core of the issue resides within the amdxdna_cmd_set_error function, which is responsible for handling command errors by inspecting the first Buffer Object in a submitted command chain. This operation inherently requires acquiring a reference count on the associated kernel object to ensure its validity during processing. Under normal operational conditions, this reference is properly released at the conclusion of the error handling routine, maintaining system stability and resource integrity. However, when the mapping of this buffer object fails within the function's execution path, the code returns early without invoking the necessary put operation to decrement the reference count. This oversight results in a persistent leak of kernel memory resources associated with that specific buffer object every time such an error condition is triggered during command processing.
While typical usage patterns for AMD XDNA acceleration do not expose this flaw due to prior caching mechanisms, there exists a distinct attack vector enabled by user-space manipulation of file descriptors and dma-buf imports. Normally, before the vulnerable code path is reached, the buffer object has already been submitted via aie2_cmdlist_fill_slot, which calls amdxdna_cmd_get_op on the buffer and caches its virtual memory address through amdxdna_gem_vmap. This caching mechanism typically prevents the need for re-resolution of the buffer's physical mapping during error handling. The vulnerability becomes reachable only when an attacker or malicious application closes the original file descriptor handle after submission and subsequently imports a dma-buf using that same identifier. If the exporter of this imported dma-buf does not implement vmap support, the kernel attempts to resolve the object again through amdxdna_gem_get_obj. In this scenario, prime_import categorizes every import as AMDXDNA_BO_SHARE, which prevents successful mapping because the necessary virtual memory mappings are absent for shared buffer objects in this context.
The operational impact of this vulnerability is primarily characterized by gradual resource exhaustion within the kernel space rather than immediate system compromise or privilege escalation. Each occurrence of the unmapped buffer object scenario results in a leaked reference count that prevents the underlying physical pages and associated metadata from being freed back to the memory manager. Over time, particularly under high-load conditions where command errors are frequent or an attacker intentionally triggers this path repeatedly, these accumulated leaks can lead to significant degradation of system performance due to increased pressure on kernel memory pools. In extreme cases, sustained leakage could contribute to out-of-memory conditions affecting not only the specific driver but potentially other subsystems relying on available contiguous memory for buffer allocations. This aligns with CWE-401, which describes a missing release of resources after effective use, highlighting the failure to properly manage dynamic memory allocation lifecycle events within kernel drivers.
From a threat modeling perspective, this vulnerability maps to ATT&CK technique T1539, specifically related to potential data exfiltration or system state manipulation through resource exhaustion if leveraged in conjunction with other vulnerabilities for denial of service attacks against critical infrastructure components relying on hardware acceleration. The flaw exploits the complex interaction between user-space handle management and kernel-side buffer object lifecycle rules, demonstrating how improper error handling paths can bypass standard cleanup procedures. Mitigation strategies must focus on ensuring that all exit points within amdxdna_cmd_set_error correctly release acquired references regardless of whether mapping succeeds or fails. Developers should implement consistent reference counting practices where every get operation is paired with a corresponding put in both success and failure branches. Additionally, enhancing validation checks to detect incompatible buffer types before attempting mappings can prevent the entry into this vulnerable code path entirely. System administrators relying on AMD XDNA acceleration hardware should apply kernel patches that address this specific logic error as soon they are available from vendor security advisories to maintain robust resource management integrity in production environments.