CVE-2021-47140

In the Linux kernel, the following vulnerability has been resolved:
iommu/amd: Clear DMA ops when switching domain Since commit 08a27c1c3ecf
(“iommu: Add support to change default domain of an iommu group”) a user
can switch a device between IOMMU and direct DMA through sysfs. This
doesn’t work for AMD IOMMU at the moment because dev->dma_ops is not
cleared when switching from a DMA to an identity IOMMU domain. The DMA
layer thus attempts to use the dma-iommu ops on an identity domain, causing
an oops: # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind #
echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type # echo
0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind … BUG: kernel NULL
pointer dereference, address: 0000000000000028 … Call Trace:
iommu_dma_alloc e1000e_setup_tx_resources e1000e_open Since
iommu_change_dev_def_domain() calls probe_finalize() again, clear the
dma_ops there like Vt-d does.