CVE-2022-48895 in Linux
Summary
by MITRE • 08/21/2024
In the Linux kernel, the following vulnerability has been resolved:
iommu/arm-smmu: Don't unregister on shutdown
Michael Walle says he noticed the following stack trace while performing a shutdown with "reboot -f". He suggests he got "lucky" and just hit the correct spot for the reboot while there was a packet transmission in flight.
Unable to handle kernel NULL pointer dereference at virtual address 0000000000000098 CPU: 0 PID: 23 Comm: kworker/0:1 Not tainted 6.1.0-rc5-00088-gf3600ff8e322 #1930 Hardware name: Kontron KBox A-230-LS (DT) pc : iommu_get_dma_domain+0x14/0x20 lr : iommu_dma_map_page+0x9c/0x254 Call trace: iommu_get_dma_domain+0x14/0x20 dma_map_page_attrs+0x1ec/0x250 enetc_start_xmit+0x14c/0x10b0 enetc_xmit+0x60/0xdc dev_hard_start_xmit+0xb8/0x210 sch_direct_xmit+0x11c/0x420 __dev_queue_xmit+0x354/0xb20 ip6_finish_output2+0x280/0x5b0 __ip6_finish_output+0x15c/0x270 ip6_output+0x78/0x15c NF_HOOK.constprop.0+0x50/0xd0 mld_sendpack+0x1bc/0x320 mld_ifc_work+0x1d8/0x4dc process_one_work+0x1e8/0x460 worker_thread+0x178/0x534 kthread+0xe0/0xe4 ret_from_fork+0x10/0x20 Code: d503201f f9416800 d503233f d50323bf (f9404c00) ---[ end trace 0000000000000000 ]---
Kernel panic - not syncing: Oops: Fatal exception in interrupt
This appears to be reproducible when the board has a fixed IP address, is ping flooded from another host, and "reboot -f" is used.
The following is one more manifestation of the issue:
$ reboot -f kvm: exiting hardware virtualization cfg80211: failed to load regulatory.db arm-smmu 5000000.iommu: disabling translation sdhci-esdhc 2140000.mmc: Removing from iommu group 11 sdhci-esdhc 2150000.mmc: Removing from iommu group 12 fsl-edma 22c0000.dma-controller: Removing from iommu group 17 dwc3 3100000.usb: Removing from iommu group 9 dwc3 3110000.usb: Removing from iommu group 10 ahci-qoriq 3200000.sata: Removing from iommu group 2 fsl-qdma 8380000.dma-controller: Removing from iommu group 20 platform f080000.display: Removing from iommu group 0 etnaviv-gpu f0c0000.gpu: Removing from iommu group 1 etnaviv etnaviv: Removing from iommu group 1 caam_jr 8010000.jr: Removing from iommu group 13 caam_jr 8020000.jr: Removing from iommu group 14 caam_jr 8030000.jr: Removing from iommu group 15 caam_jr 8040000.jr: Removing from iommu group 16 fsl_enetc 0000:00:00.0: Removing from iommu group 4 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000002, GFSYNR1 0x00000429, GFSYNR2 0x00000000 fsl_enetc 0000:00:00.1: Removing from iommu group 5 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000002, GFSYNR1 0x00000429, GFSYNR2 0x00000000 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000000, GFSYNR1 0x00000429, GFSYNR2 0x00000000 fsl_enetc 0000:00:00.2: Removing from iommu group 6 fsl_enetc_mdio 0000:00:00.3: Removing from iommu group 8 mscc_felix 0000:00:00.5: Removing from iommu group 3 fsl_enetc 0000:00:00.6: Removing from iommu group 7 pcieport 0001:00:00.0: Removing from iommu group 18 arm-smmu 5000000.iommu: Blocked unknown Stream ID 0x429; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications arm-smmu 5000000.iommu: GFSR 0x00000002, GFSYNR0 0x00000000, GFSYNR1 0x00000429, GFSYNR2 0x00000000 pcieport 0002:00:00.0: Removing from iommu group 19 Unable to handle kernel NULL pointer dereference at virtual address 00000000000000a8 pc : iommu_get_dma_domain+0x14/0x20 lr : iommu_dma_unmap_page+0x38/0xe0 Call trace: iommu_get_dma_domain+0x14/0x20 dma_unmap_page_attrs+0x38/0x1d0 en ---truncated---
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Analysis
by VulDB Data Team • 02/17/2026
The vulnerability described in CVE-2022-48895 affects the Linux kernel's IOMMU implementation, specifically within the ARM SMMU (System Memory Management Unit) driver. This issue manifests as a kernel NULL pointer dereference during system shutdown operations, particularly when using the force reboot command reboot -f. The problem occurs when the system attempts to shut down while IOMMU translation is still active, and network packet transmission is in progress, creating a race condition between device removal and ongoing DMA operations. The stack trace shows the kernel crashing in iommu_get_dma_domain function, indicating that a null pointer access occurs when the system tries to retrieve DMA domain information after devices have been removed from the IOMMU group. This vulnerability is classified under CWE-476 as a NULL pointer dereference, which represents a critical flaw in kernel memory management and device handling. The issue is particularly dangerous because it can cause system crashes and potential data loss during critical shutdown procedures, violating the fundamental reliability requirements for embedded and server systems.
The technical root cause stems from improper synchronization between IOMMU device unregistration and ongoing DMA operations during system shutdown. When the system begins the shutdown sequence, the ARM SMMU driver attempts to unregister devices from the IOMMU group while device drivers are still processing network packets through DMA operations. This creates a scenario where iommu_get_dma_domain is called on a device that has already been partially or fully unregistered, resulting in a NULL pointer dereference at virtual address 0x0000000000000098. The error occurs in the context of network driver enetc_start_xmit which is attempting to map pages for DMA transmission while the IOMMU subsystem is in the process of cleaning up. The vulnerability is amplified by the fact that the system is under network load with ping flooding, which increases the likelihood of packet transmission during the shutdown process. This scenario aligns with ATT&CK technique T1490 which involves system shutdown/reboot to disrupt services, and T1566 which covers social engineering through network-based attacks. The IOMMU subsystem's failure to properly handle device removal during active operations represents a breakdown in kernel device management protocols.
The operational impact of this vulnerability is severe and can result in complete system crashes during shutdown procedures, which is particularly concerning for embedded systems, network infrastructure, and mission-critical applications that rely on predictable system behavior. When triggered, the vulnerability can cause a kernel panic that prevents normal system shutdown, potentially leading to data corruption, loss of network connectivity, and service disruption. The vulnerability is particularly dangerous in environments where force reboot commands are used frequently, such as automated testing environments, production servers, or embedded devices that may experience unexpected power loss or forced restarts. The intermittent nature of the issue means it may not be consistently reproducible, but when it occurs, it can cause significant operational downtime. Systems running the affected kernel versions with ARM SMMU hardware are at risk, especially those with active network traffic during shutdown operations, making this vulnerability a critical concern for networked embedded systems and server platforms using ARM-based processors.
Mitigation strategies for CVE-2022-48895 involve both immediate system-level fixes and long-term architectural improvements. The primary solution is to update to a kernel version that includes the patch addressing this specific IOMMU shutdown race condition, which was resolved by ensuring proper device unregistration sequence and preventing access to unregistered IOMMU domains. System administrators should implement proper shutdown procedures that avoid force reboot commands when possible, and instead use graceful shutdown sequences that allow device drivers to properly clean up before IOMMU operations begin. For systems where immediate kernel updates are not feasible, implementing additional monitoring and logging around shutdown procedures can help detect and respond to such failures. The fix addresses the underlying issue by ensuring that IOMMU domain lookups are properly synchronized with device removal operations, preventing the NULL pointer dereference that occurs during shutdown sequences. Organizations should also review their network infrastructure configurations to minimize active packet transmission during system shutdown operations, and consider implementing proper system health checks that can detect and prevent shutdown operations when critical network traffic is detected. This vulnerability highlights the importance of proper kernel device management and the need for thorough testing of shutdown procedures in embedded and networked systems, aligning with security best practices outlined in NIST SP 800-128 and ISO/IEC 27001 requirements for system reliability and availability.