CVE-2026-98964 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
nvmet: use the local P2P device on metadata allocation failure
nvmet_req_alloc_p2pmem_sgls() assigns req->p2p_dev only after the data and metadata SGL allocations succeed. If the data allocation succeeds but the metadata allocation fails, out_free_sg passes req->p2p_dev to pci_p2pmem_free_sgl() before that assignment has taken place.
Pass the local p2p_dev argument instead, so cleanup uses the same PCI device as the successful data allocation.
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Analysis
by VulDB Data Team • 10/23/2026
The Linux kernel's NVMe target subsystem contains a logic error in its peer-to-peer direct memory access resource management path that can lead to improper resource release and potential system instability. This vulnerability specifically affects the function nvmet_req_alloc_p2pmem_sgls, which is responsible for allocating scatter-gather lists using P2P memory for both data and metadata operations during NVMe request processing. The core technical flaw lies in the sequencing of variable assignment versus error handling logic within this allocation routine. Specifically, the code assigns the req->p2p_dev pointer only after both the data segment list and the metadata segment list allocations have successfully completed. However, if the initial data allocation succeeds but the subsequent metadata allocation fails, the kernel's cleanup path is triggered via out_free_sg to prevent memory leaks or resource exhaustion.
In this failure scenario, the cleanup routine incorrectly passes req->p2p_dev to pci_p2pmem_free_sgl because that pointer has not yet been updated with the correct device reference from the successful data allocation phase. Consequently, the system attempts to free P2P memory using an uninitialized or stale device identifier rather than the actual PCI device associated with the successfully allocated data buffers. This mismatch can result in a use-after-free condition where resources are freed against incorrect hardware contexts, potentially leading to kernel panics, data corruption within the NVMe subsystem, or denial of service for subsequent I/O operations targeting that specific request structure. The issue highlights a critical gap in defensive programming practices regarding error paths and resource tracking consistency during multi-stage allocation processes involving peer-to-peer DMA capabilities.
From an industry standards perspective, this vulnerability aligns with CWE-416, Use After Free, as the cleanup logic interacts with memory resources using invalid or incorrect device context pointers after partial success. It also relates to CWE-755, Improper Handling of Exceptional Conditions, because the error handling path fails to maintain state consistency when an intermediate allocation step fails. In terms of MITRE ATT&CK mapping, while this is primarily a stability and reliability issue rather than a direct exploitation vector for privilege escalation, it falls under T1499, Endpoint Denial of Service, as repeated occurrences could destabilize the host system or disrupt NVMe target services available to initiators. The vulnerability underscores the importance of ensuring that resource tracking variables are updated atomically or immediately upon successful acquisition, regardless of subsequent allocation outcomes for related resources within the same transaction block.
Mitigation strategies involve applying the upstream kernel patch that corrects the argument passed during cleanup by using a local p2p_dev variable instead of req->p2p_dev in the error path. This ensures that pci_p2pmem_free_sgl receives the correct PCI device reference corresponding to the data allocation that actually succeeded, thereby maintaining proper resource ownership and preventing invalid memory operations. System administrators should ensure their Linux kernels are updated with this fix applied, particularly for systems running NVMe target configurations where peer-to-peer DMA is enabled or utilized for performance optimization. Regular auditing of kernel logs for P2P-related errors can help detect any residual instability before it impacts production workloads.