CVE-2026-90319 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
rapidio: clear mport->net when rio_add_net() fails
rio_alloc_net() stores the newly allocated rio_net in mport->net before rio_scan_alloc_net() registers the device.
If rio_add_net() fails, rio_scan_alloc_net() drops the device reference with put_device(), which releases the rio_net through the device release callback. However, mport->net is left pointing at the freed object.
A later mport unregister path can then dereference the dangling mport->net pointer and may try to free the same rio_net again.
Clear mport->net in the rio_add_net() failure path, matching the cleanup done for the destID table allocation failure path.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel RapidIO subsystem contains a use-after-free vulnerability arising from improper resource management during network initialization failures. The core of this issue lies within the rio_scan_alloc_net function, which is responsible for setting up a new RapidIO network context associated with a master port device. During normal operation, the code allocates a rio_net structure and immediately assigns it to the mport->net pointer before proceeding to register the device via rio_add_net(). This early assignment creates a dependency where the master port's state reflects an active network association even if subsequent registration steps fail.
The vulnerability manifests when rio_add_net() encounters an error condition, such as resource exhaustion or configuration conflicts, and returns a failure code. In this scenario, the kernel attempts to unwind the partially completed operation by calling put_device(), which decrements the reference count of the device object. Because the rio_net was linked to the device structure prior to registration, its release callback is triggered upon the final drop in references, leading to the deallocation and freeing of the rio_net memory block. However, the code fails to nullify the mport->net pointer after this cleanup sequence completes. Consequently, the master port retains a stale reference pointing to memory that has been returned to the kernel's allocator for reuse by other subsystems or processes.
This dangling pointer creates a critical security risk during subsequent lifecycle events of the master port device. If the system attempts to unregister or remove the mport later in its operational lifetime, it traverses cleanup paths that assume valid network structures are present. Specifically, these paths may attempt to dereference mport->net to perform further teardown operations or free associated resources. Since the pointer now references freed memory, this access constitutes a use-after-free condition. Depending on how the kernel allocator has repurposed the overwritten memory region, an attacker who can influence allocation patterns might exploit this to achieve arbitrary code execution by controlling the contents of the reused memory block, or cause a denial of service through a kernel panic resulting from invalid pointer dereference and subsequent page fault handling failures.
From a classification perspective, this vulnerability aligns with CWE-416, Use After Free, as it involves accessing memory after it has been freed due to incorrect state management. It also relates to CWE-755, Improper Handling of Exceptional Conditions, because the error path fails to maintain consistent object states when initialization routines fail. In terms of MITRE ATT&CK mapping, this flaw could potentially be leveraged in techniques associated with T1068, Exploitation for Privilege Escalation, if an attacker can trigger the specific failure condition and manipulate memory allocation to hijack control flow during the subsequent dereference event.
The resolution involves modifying the error handling logic within rio_scan_alloc_net() to explicitly clear the mport->net pointer when rio_add_net() fails. This change ensures that any future attempts to access this field will encounter a null reference rather than a dangling one, thereby preventing invalid memory accesses and potential exploitation vectors. To mitigate similar issues in related subsystems, developers should enforce strict adherence to cleanup protocols where all pointers associated with allocated resources are invalidated immediately upon resource release or failure during initialization sequences. System administrators can reduce exposure by ensuring kernel updates are applied promptly once patches addressing this specific RapidIO flaw are available through their distribution channels.