CVE-2024-46761 in Linux
Summary
by MITRE • 09/18/2024
In the Linux kernel, the following vulnerability has been resolved:
pci/hotplug/pnv_php: Fix hotplug driver crash on Powernv
The hotplug driver for powerpc (pci/hotplug/pnv_php.c) causes a kernel crash when we try to hot-unplug/disable the PCIe switch/bridge from the PHB.
The crash occurs because although the MSI data structure has been released during disable/hot-unplug path and it has been assigned with NULL, still during unregistration the code was again trying to explicitly disable the MSI which causes the NULL pointer dereference and kernel crash.
The patch fixes the check during unregistration path to prevent invoking pci_disable_msi/msix() since its data structure is already freed.
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Analysis
by VulDB Data Team • 04/06/2026
The vulnerability described in CVE-2024-46761 represents a critical kernel panic condition within the Linux kernel's powerpc architecture hotplug subsystem. This issue specifically affects the powernv platform where the pci/hotplug/pnv_php.c driver experiences a system crash during PCIe switch or bridge hot-unplug operations from the PHB (PCIe Hot Plug Bridge). The flaw manifests as a null pointer dereference during the driver's cleanup phase, which occurs when attempting to disable MSI (Message Signaled Interrupts) or MSI-X interrupts after the underlying data structures have already been freed. The vulnerability impacts the kernel's ability to safely manage hardware resources during dynamic system reconfiguration, potentially leading to complete system instability and service disruption.
The technical root cause of this vulnerability stems from improper state management within the hotplug driver's unregistration path. During normal operation, when a PCIe device is disabled or hot-unplugged, the MSI data structures are correctly released and set to NULL. However, the subsequent cleanup code fails to properly check whether these structures have already been freed before attempting to invoke pci_disable_msi() or pci_disable_msix() functions. This oversight creates a scenario where the driver attempts to operate on freed memory structures, resulting in a NULL pointer dereference that triggers a kernel oops and system crash. The flaw demonstrates a classic improper resource management issue that violates fundamental kernel safety principles and proper memory lifecycle management practices.
The operational impact of this vulnerability extends beyond simple system crashes to encompass broader reliability concerns for powerpc-based systems, particularly those running in enterprise or data center environments where dynamic hardware reconfiguration is common. Systems utilizing powernv platforms may experience unexpected service interruptions when administrators attempt routine hardware maintenance or configuration changes involving PCIe switches and bridges. The vulnerability could be exploited by malicious actors to cause denial of service conditions, potentially leading to extended downtime for critical infrastructure components. Additionally, the crash occurs at kernel level, making it impossible to recover gracefully, which means that any automated systems relying on hotplug functionality would face complete service disruption during the affected operations.
Mitigation strategies for this vulnerability should prioritize the immediate application of the provided kernel patch which corrects the conditional logic in the unregistration path to prevent invocation of MSI disable functions on already-freed data structures. System administrators should monitor kernel release notes and apply security updates promptly to ensure protection against this specific null pointer dereference issue. Organizations running powernv-based systems should implement monitoring solutions to detect potential crashes during PCIe hotplug operations and establish recovery procedures for systems that may experience unexpected kernel panics. The fix aligns with best practices for kernel memory management and follows the principle of defensive programming by ensuring proper state validation before resource operations. This vulnerability highlights the importance of rigorous testing for hotplug and device management subsystems in kernel development, particularly in complex architectures like powerpc where hardware abstraction layers must maintain strict consistency between software state and hardware reality. The issue demonstrates the critical nature of proper resource lifecycle management and the potential for seemingly simple code paths to introduce catastrophic failures in operating system kernels.