CVE-2022-48895: iommu/arm-smmu: Don't unregister on shutdown
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---
CVSS v3.1: 5.5