CVE-2021-47554

In the Linux kernel, the following vulnerability has been resolved:
vdpa_sim: avoid putting an uninitialized iova_domain The system will crash
if we put an uninitialized iova_domain, this could happen when an error
occurs before initializing the iova_domain in vdpasim_create(). BUG: kernel
NULL pointer dereference, address: 0000000000000000 … RIP:
0010:__cpuhp_state_remove_instance+0x96/0x1c0 … Call Trace: <TASK>
put_iova_domain+0x29/0x220 vdpasim_free+0xd1/0x120 [vdpa_sim]
vdpa_release_dev+0x21/0x40 [vdpa] device_release+0x33/0x90
kobject_release+0x63/0x160 vdpasim_create+0x127/0x2a0 [vdpa_sim]
vdpasim_net_dev_add+0x7d/0xfe [vdpa_sim_net]
vdpa_nl_cmd_dev_add_set_doit+0xe1/0x1a0 [vdpa]
genl_family_rcv_msg_doit+0x112/0x140 genl_rcv_msg+0xdf/0x1d0 … So we must
make sure the iova_domain is already initialized before put it. In
addition, we may get the following warning in this case: WARNING: …
drivers/iommu/iova.c:344 iova_cache_put+0x58/0x70 So we must make sure the
iova_cache_put() is invoked only if the iova_cache_get() is already
invoked. Let’s fix it together.