Subject: CVE-2021-47554: vdpa_sim: avoid putting an uninitialized iova_domain

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

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.

The Linux kernel CVE team has assigned CVE-2021-47554 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.13 with commit 4080fc106750 and fixed in 5.15.6 with commit e4d58ac67e63
	Issue introduced in 5.13 with commit 4080fc106750 and fixed in 5.16 with commit bb93ce4b150d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47554
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/vdpa/vdpa_sim/vdpa_sim.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/e4d58ac67e63727aa45a4a26185876f598e8b3dd
	https://git.kernel.org/stable/c/bb93ce4b150dde79f58e34103cbd1fe829796649