CVE-2026-93151 in Linux
Summary
by MITRE • 09/18/2026
In the Linux kernel, the following vulnerability has been resolved:
nvmet-rdma: fix response resource leak on queue teardown
When an nvme target with rdma transport is removed while I/Os are in flight, a response can be posted but its send completion is never delivered before the connection is torn down. As a result nvmet_rdma_send_done() and nvmet_rdma_release_rsp() are never called for the response, and this leaks the allocated RDMA read/write context and request SGLs.
These leaks are recreated by running blktests nvme/061 with the rdma transport and the siw driver. Kernel kmemleak feature reports them as follows:
unreferenced object 0xffff88812bc490c0 (size 32): comm "kworker/2:1H", pid 409, jiffies 4307744490 backtrace (crc 89afd339): __kmalloc_noprof+0x5f9/0x890 sgl_alloc_order+0x7b/0x380 nvmet_req_alloc_sgls+0x290/0x4f0 [nvmet]
nvmet_rdma_map_sgl_keyed+0x241/0x12e0 [nvmet_rdma]
nvmet_rdma_handle_command+0x73e/0xb80 [nvmet_rdma]
__ib_process_cq+0x149/0x4c0 [ib_core]
ib_cq_poll_work+0x49/0x160 [ib_core]
process_one_work+0x8b2/0x1640 worker_thread+0x5fd/0xfe0 kthread+0x367/0x460 ret_from_fork+0x655/0x9d0 ret_from_fork_asm+0x1a/0x30
unreferenced object 0xffff88814bd05e80 (size 64): comm "kworker/3:1H", pid 148, jiffies 4295195428 backtrace (crc e35510cb): __kmalloc_noprof+0x5f9/0x890 rdma_rw_ctx_init+0x333/0x1fa0 [ib_core]
nvmet_rdma_map_sgl_keyed+0x5c8/0x12e0 [nvmet_rdma]
nvmet_rdma_handle_command+0x73e/0xb80 [nvmet_rdma]
__ib_process_cq+0x149/0x4c0 [ib_core]
ib_cq_poll_work+0x49/0x160 [ib_core]
process_one_work+0x8b2/0x1640 worker_thread+0x5fd/0xfe0 kthread+0x367/0x460 ret_from_fork+0x655/0x9d0 ret_from_fork_asm+0x1a/0x30
To avoid the memory leaks, reclaim the memory of the in-flight responses when the queue QP is torn down. Call nvmet_rdma_free_rsp_resources() that frees up the RDMA read/write context and the request SGLs of such responses.
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Analysis
by VulDB Data Team • 09/18/2026
The Linux kernel vulnerability identified as a resource leak within the NVMe over Fabrics (nvme) target subsystem specifically affects the Remote Direct Memory Access (RDMA) transport implementation. This issue arises during the lifecycle management of queue pairs when an nvmet-rdma device is removed while input/output operations are still actively in flight. In normal operation, RDMA-based storage targets rely on a completion mechanism where hardware signals the CPU that data transfer has finished via send or receive completions. However, under specific teardown conditions, this signaling chain breaks down. When the connection is forcibly torn down before these asynchronous operations complete, the kernel fails to invoke critical cleanup functions such as nvmet_rdma_send_done and nvmet_rdma_release_rsp for pending responses. This failure prevents the proper release of allocated resources associated with those in-flight requests, leading to a persistent memory leak that degrades system stability over time or under high churn conditions involving device removal and re-addition cycles.
From a technical perspective, the flaw lies in the teardown sequence of the Queue Pair (QP) within the nvmet-rdma driver. The kernel allocates Scatter-Gather Lists SGLs to map user-space buffers into kernel space for RDMA operations, along with initializing RDMA read/write contexts that manage the data transfer state. These allocations are tracked by the kernel memory allocator and reported via tools like kmemleak when they become unreferenced but not freed. The backtrace provided in the vulnerability report indicates that these objects originate from standard kmalloc routines invoked during SGL allocation and context initialization within nvmet_rdma_map_sgl_keyed. Because the completion handler is never triggered due to the abrupt connection termination, the reference counts for these structures are never decremented, leaving them as unreferenced memory blocks in kernel space. This represents a classic resource management error where cleanup logic is not properly integrated into all exit paths of the driver state machine.
The operational impact of this vulnerability is primarily related to system stability and resource exhaustion rather than immediate security exploitation like privilege escalation or remote code execution. However, as a denial-of-service vector, it poses significant risks in production environments that utilize NVMe over RDMA for high-performance storage networking. If an attacker or automated process can trigger repeated removals of nvmet-rdma targets while maintaining active I/O streams, they can induce continuous memory leaks within the kernel space. Over time, this consumes available physical and virtual memory resources allocated to the kernel slab caches. Eventually, this leads to out-of-memory conditions that may cause system hangs, crashes, or unpredictable behavior in dependent services relying on stable storage connectivity. The issue is particularly relevant for cloud infrastructure and data center environments where dynamic scaling of NVMe targets over RDMA networks is common practice.
To mitigate this vulnerability, the Linux kernel developers have implemented a fix that ensures proper cleanup of resources associated with in-flight responses during queue teardown procedures. Specifically, the patch introduces calls to nvmet_rdma_free_rsp_resources when the Queue Pair is being torn down. This function explicitly frees up the RDMA read/write contexts and request Scatter-Gather Lists for any pending responses that have not yet completed. By integrating this cleanup logic into the teardown path, the driver guarantees that all allocated memory associated with active I/O operations is released regardless of whether hardware completions are delivered before disconnection. Administrators should apply kernel updates containing this patch to prevent resource leaks in RDMA-based NVMe target deployments. Regular monitoring of kernel memory usage and utilization of debugging tools like kmemleak can help detect residual issues during testing phases prior to widespread deployment.
This vulnerability aligns with Common Weakness Enumeration CWE-401, which describes a missing release of memory after successful allocation, leading to resource exhaustion. It also relates to improper cleanup procedures often categorized under CWE-755 in the context of failure to handle exceptional conditions or state transitions correctly within device drivers. In terms of adversarial tactics, while not directly exploitable for initial access, this flaw supports Denial-of-Service scenarios consistent with MITRE ATT&CK technique T1499 Endpoint Denial of Service if leveraged systematically against storage infrastructure components. The fix emphasizes the importance of robust state management in kernel drivers handling asynchronous hardware interactions, ensuring that all allocated resources are reclaimed during any form of connection termination to maintain system integrity and availability.