Subject: CVE-2022-48828: NFSD: Fix ia_size underflow

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

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

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

NFSD: Fix ia_size underflow

iattr::ia_size is a loff_t, which is a signed 64-bit type. NFSv3 and
NFSv4 both define file size as an unsigned 64-bit type. Thus there
is a range of valid file size values an NFS client can send that is
already larger than Linux can handle.

Currently decode_fattr4() dumps a full u64 value into ia_size. If
that value happens to be larger than S64_MAX, then ia_size
underflows. I'm about to fix up the NFSv3 behavior as well, so let's
catch the underflow in the common code path: nfsd_setattr().

The Linux kernel CVE team has assigned CVE-2022-48828 to this issue.

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

	Fixed in 5.10.220 with commit 38d02ba22e43
	Fixed in 5.15.24 with commit 8e0ecaf7a7e5
	Fixed in 5.16.10 with commit da22ca1ad548
	Fixed in 5.17 with commit e6faac3f58c7

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-2022-48828
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/nfsd/vfs.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/38d02ba22e43b6fc7d291cf724bc6e3b7be6626b
	https://git.kernel.org/stable/c/8e0ecaf7a7e57b30284d6b3289cc436100fadc48
	https://git.kernel.org/stable/c/da22ca1ad548429d7822011c54cfe210718e0aa7
	https://git.kernel.org/stable/c/e6faac3f58c7c4176b66f63def17a34232a17b0e