CVE-2022-49704: 9p: fix fid refcount leak in v9fs_vfs_get_link

CVE-2022-49704: 9p: fix fid refcount leak in v9fs_vfs_get_link

[Greg Kroah-Hartman]

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

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

9p: fix fid refcount leak in v9fs_vfs_get_link

we check for protocol version later than required, after a fid has
been obtained. Just move the version check earlier.

The Linux kernel CVE team has assigned CVE-2022-49704 to this issue.


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

	Issue introduced in 5.11 with commit 6636b6dcc3db2258cd0585b8078c1c225c4b6dde and fixed in 5.15.51 with commit f0126bcaee81dabc1926012126aa74caa03a4c6e
	Issue introduced in 5.11 with commit 6636b6dcc3db2258cd0585b8078c1c225c4b6dde and fixed in 5.18.8 with commit e7b6d622bd812013eb39c8f4cd65b7ee8ede1e02
	Issue introduced in 5.11 with commit 6636b6dcc3db2258cd0585b8078c1c225c4b6dde and fixed in 5.19 with commit e5690f263208c5abce7451370b7786eb25b405eb

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-2022-49704
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:
	fs/9p/vfs_inode.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/f0126bcaee81dabc1926012126aa74caa03a4c6e
	https://git.kernel.org/stable/c/e7b6d622bd812013eb39c8f4cd65b7ee8ede1e02
	https://git.kernel.org/stable/c/e5690f263208c5abce7451370b7786eb25b405eb