CVE-2022-50058

In the Linux kernel, the following vulnerability has been resolved:

vdpasimblk: set number of address spaces and virtqueue groups

Commit bda324fd037a ("vdpasim: control virtqueue support") added two new fields (nas, ngroups) to vdpasimdevattr, but we forgot to initialize them for vdpasimblk.

When creating a new vdpasimblk device this causes the kernel to panic in this way:    $ vdpa dev add mgmtdev vdpasimblk name blk0    BUG: kernel NULL pointer dereference, address: 0000000000000030    ...    RIP: 0010:vhostiotlbaddrangectx+0x41/0x220 [vhostiotlb]    ...    Call Trace:     <TASK>     vhostiotlbaddrange+0x11/0x800 [vhostiotlb]     vdpasimmaprange+0x91/0xd0 [vdpasim]     vdpasimalloccoherent+0x56/0x90 [vdpasim]     ...

This happens because vdpasim->iommu[0] is not initialized when dev_attr.nas is 0.

Let's fix this issue by initializing both (nas, ngroups) to 1 for vdpasimblk.