CVE-2026-64462 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
PCI: altera: Fix resource leaks on probe failure
The chained IRQ handler is set during probe, but is only removed during the driver remove(). If pci_host_probe() fails, the handler and INTx IRQ domain remain set even though the devm-managed host bridge storage containing struct altera_pcie will be released, leaving the handler with a stale data pointer.
Interrupts are also enabled before pci_host_probe() is called. If probe fails after that point, the controller interrupt source should be disabled before the chained handler and INTx domain are removed.
So set the chained handler only after the INTx domain has been created. Disable controller interrupts during IRQ teardown, and tear the IRQ setup down if pci_host_probe() fails.
[mani: commit log]
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Analysis
by VulDB Data Team • 07/25/2026
This vulnerability resides in the Linux kernel's PCI subsystem, specifically within the Altera PCIe driver implementation where improper resource management leads to persistent interrupt handler references and potential system instability. The flaw manifests when the driver probe function encounters failure during the initialization sequence, leaving behind stale interrupt handler references that can cause undefined behavior when subsequent operations attempt to access freed memory structures. This represents a classic resource leak scenario where dynamic allocations occur without proper cleanup mechanisms in error paths.
The technical root cause stems from the improper ordering of interrupt setup operations within the driver's probe routine. The chained IRQ handler is configured before the INTx IRQ domain creation, creating a situation where if pci_host_probe() fails at any point after handler registration but before domain establishment, the system maintains references to uninitialized or improperly configured interrupt handling structures. This violates fundamental resource management principles and creates dangling pointer scenarios that can lead to kernel crashes or privilege escalation opportunities.
From an operational perspective, this vulnerability exposes systems to potential denial of service conditions where the PCIe controller becomes unstable following failed probe attempts. The persistence of stale interrupt handlers means that subsequent hardware enumeration or system operations may encounter corrupted interrupt state information, potentially causing cascading failures throughout the system's PCI subsystem. Attackers could theoretically exploit this by repeatedly triggering probe failures to accumulate multiple stale handler references, leading to unpredictable system behavior.
The vulnerability aligns with CWE-404, which addresses resource leaks in software systems, and demonstrates poor error handling practices in kernel space programming where cleanup operations are not properly synchronized with allocation sequences. From an ATT&CK framework perspective, this could enable privilege escalation or denial of service through improper interrupt management, potentially falling under techniques related to system binary modification or privilege escalation via kernel vulnerabilities.
The fix addresses these issues by reordering the initialization sequence to ensure that the chained handler is only registered after successful creation of the INTx IRQ domain, thereby eliminating the window where stale references can exist. Additionally, controller interrupts are disabled during the IRQ teardown process before removing handler registrations, preventing further interrupt processing from attempting to reference freed memory structures. The implementation also ensures that all interrupt setup operations are properly torn down if pci_host_probe() fails, maintaining proper resource cleanup even in error conditions. This approach follows best practices for kernel driver development where resource management must be robust against all execution paths, including failure scenarios.
The solution implements proper devm (device managed) resource handling patterns where automatic cleanup occurs regardless of whether probe succeeds or fails. The fix ensures that interrupt domain creation and handler registration occur as a coordinated unit, preventing partial initialization states from persisting in memory. This remediation aligns with kernel development standards requiring proper error path handling and resource cleanup to prevent system instability and maintain the integrity of hardware abstraction layers.
The mitigation strategy focuses on defensive programming practices within kernel space drivers, emphasizing that all dynamic allocations must have corresponding deallocation mechanisms regardless of execution flow. The implementation demonstrates proper use of device managed resources and careful ordering of initialization sequences to prevent partial state accumulation. This vulnerability class highlights the importance of comprehensive error handling in kernel modules where improper cleanup can leave systems in inconsistent states, potentially enabling exploitation through resource exhaustion or memory corruption attacks.
The fix represents a fundamental improvement in driver robustness by ensuring that interrupt subsystem cleanup occurs properly even when probe operations fail. This prevents the accumulation of stale interrupt handler references that could otherwise compromise system stability over time, particularly in environments where PCIe devices are frequently enumerated or hot-plugged. The remediation approach follows established kernel development practices for managing complex hardware initialization sequences and demonstrates proper consideration of error conditions throughout the driver lifecycle.