CVE-2026-89974 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
nvme-fc: fix double free of fabrics options when nvme_add_ctrl() fails
nvmf_create_ctrl() owns the fabrics options and frees them whenever ->create_ctrl() returns an error, so a transport must not free them on its own error paths. nvme-fc tracks this by testing ctrl->ctrl.opts in nvme_fc_ctrl_free(), which requires nvme_fc_init_ctrl() to clear that pointer on every error exit.
The coupling is implicit, and commit 1a9e218195a5 ("nvme: split device add from initialization") broke it by adding a second error exit. When nvme_add_ctrl() fails, nvme_fc_init_ctrl() jumps to out_put_ctrl:, past the "ctrl->ctrl.opts = NULL" that only sits on the fail_ctrl: path, so nvme_fc_ctrl_free() frees the options and nvmf_create_ctrl() frees them a second time:
BUG: KASAN: slab-use-after-free in nvmf_free_options+0x30/0x190 nvmf_free_options+0x30/0x190 drivers/nvme/host/fabrics.c:1284 nvmf_create_ctrl drivers/nvme/host/fabrics.c:1374 [inline]
Freed by task 5534: nvme_fc_ctrl_free drivers/nvme/host/fc.c:2374 [inline]
nvme_fc_init_ctrl+0xe17/0x1450 drivers/nvme/host/fc.c:3605
nvme_add_ctrl() fails when dev_set_name() cannot allocate, so this is reachable under memory pressure or fault injection. Without KASAN the options are freed twice.
Rather than clear the pointer on the second exit as well, derive ownership the way nvme-tcp, nvme-rdma and nvme-loop do, from list membership: their free_ctrl leaves the options alone unless the controller made it onto the transport list.
The list cannot simply be populated on the success path as it is there. nvme-fc runs the initial connect synchronously via flush_delayed_work(), and the controller has to be reachable on rport->ctrl_list for the whole of it: nvme_fc_unregister_remoteport() needs to find it to signal connectivity loss, nvme_fc_match_disconn_ls() matches an incoming Disconnect Association LS against ctrl->association_id, which is only assigned during that window, nvme_fc_resume_controller() needs it on remoteport re-registration, and nvme_fc_existing_controller() uses it to reject a duplicate connect racing the one in flight.
Keep the insertion where it is and add a fail_unlist: label, falling into fail_ctrl:, for the error paths that run after it. The earlier error paths never reach the insertion and keep using fail_ctrl: directly, so the list is only touched where the controller is actually on it.
nvme_fc_ctrl_free() cannot use the plain "goto free_ctrl" the other transports use, because it still has to put_device(), release the rport reference and free the ida entry for resources taken before the insertion. Sample list_empty() under rport->lock instead.
ctrl->ctrl.opts also stays valid for the whole teardown now. That is not the bug being fixed, but it removes some fragility around the old idiom: nvme_free_ctrl() calls nvme_auth_free() before ->free_ctrl(), and ctrl_max_dhchaps() dereferences ctrl->opts without a NULL check when ctrl->dhchap_ctxs is set, which nvme-fc permits since NVMF_ALLOWED_OPTS allows the dhchap options. The nvme sysfs attributes that dereference ctrl->opts, such as hostnqn and address, evaluate their is_visible() test once at device_add() time and stay readable until cdev_device_del().
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel vulnerability identified in the NVMe over Fabrics Fibre Channel transport driver involves a critical double-free memory corruption issue within the controller initialization sequence. This flaw stems from an implicit ownership contract between the core fabrics subsystem and specific transport implementations regarding the lifecycle management of configuration options structures. Specifically, the nvmf_create_ctrl function assumes exclusive ownership of these fabric options and is responsible for freeing them upon any error during controller creation. However, the nvme-fc driver previously attempted to manage this resource independently by clearing a pointer in its own cleanup path. This design relied on strict adherence to a single exit point structure that was inadvertently broken by commit 1a9e218195a5, which split device addition from initialization and introduced an additional error handling branch. When nvme_add_ctrl fails due to resource allocation issues such as those triggered by memory pressure or fault injection scenarios, the control flow jumps past the code responsible for nullifying the options pointer in the transport layer. Consequently, when the controller structure is subsequently freed, both the transport driver and the core fabrics subsystem attempt to deallocate the same memory region, resulting in a slab-use-after-free condition that can lead to kernel panics or potential exploitation vectors involving arbitrary write primitives if the double-freed memory is reallocated before being accessed again.
From a technical perspective, this vulnerability represents a classic resource management error where ownership semantics are not explicitly defined across module boundaries. The root cause lies in the asynchronous nature of NVMe over Fabrics connections and the specific requirements for controller visibility during the connection establishment phase. Unlike other transports such as nvme-tcp or nvme-rdma which derive ownership from list membership, nvme-fc requires the controller to be present on a remote port control list throughout the synchronous initial connect process facilitated by flush_delayed_work. This presence is mandatory because subsequent operations like unregistering remote ports, matching disconnect association logical units against controller identifiers, resuming controllers during re-registration, and preventing duplicate connection races all depend on locating the active controller structure via this list. The previous implementation failed to account for error paths that occurred after the controller was added to this list but before successful initialization completed, leading to a state where the options pointer remained non-null despite an impending failure, thereby triggering the double free when both layers attempted cleanup.
The operational impact of this vulnerability is significant as it compromises system stability under conditions of high load or memory scarcity. Since nvme_add_ctrl failures often occur during device name allocation, which can fail if the kernel cannot allocate sufficient contiguous memory, this bug is reachable in production environments experiencing resource contention. An attacker with local access could potentially trigger these error paths through repeated connection attempts combined with memory pressure techniques to induce the specific failure condition required for the double free. While immediate exploitation might be complex due to the need to synchronize race conditions and manage kernel heap state, the presence of a use-after-free vulnerability in core storage subsystems provides a valuable primitive for further privilege escalation or denial-of-service attacks against critical infrastructure components that rely on NVMe over Fabrics connectivity.
To mitigate this issue, the fix restructures the error handling logic to align with established patterns used by other NVMe transport drivers while preserving the necessary list membership requirements specific to Fibre Channel operations. Instead of relying on a simple pointer nullification at a single exit point, the solution introduces a fail_unlist label that handles cleanup for controllers already inserted into the remote port control list before falling through to standard controller teardown procedures. This ensures that resources allocated prior to list insertion are correctly released without interfering with the options structure managed by the core fabrics layer. Additionally, nvme_fc_ctrl_free is modified to check if the controller remains on the active list using a sample under lock protection rather than blindly freeing associated data structures. This approach eliminates the ambiguity of ownership and ensures that memory deallocation occurs exactly once per allocation event.
This vulnerability aligns with CWE-415 Double Free, which describes the condition where an application frees a block of memory twice, leading to heap corruption and potential code execution. Furthermore, it relates to CWE-762 Mismatched Memory Management Routines, as the disconnect between who allocates resources and who is responsible for freeing them created inconsistent state management across module boundaries. In terms of ATT&CK mapping, this type of kernel memory corruption vulnerability can be leveraged in post-exploitation phases to escalate privileges from user space to ring zero, facilitating lateral movement or persistence within a compromised system. The resolution emphasizes the importance of explicit ownership models and robust error path coverage in complex subsystems like storage drivers where multiple components interact asynchronously. By adopting list-based ownership derivation similar to other transports while respecting the unique synchronization requirements of Fibre Channel NVMe connections, the kernel now maintains memory safety even under adverse conditions such as severe memory pressure or injected faults during device initialization sequences.