CVE-2021-46934: i2c: validate user data in compat ioctl

CVE-2021-46934: i2c: validate user data in compat ioctl

[Greg Kroah-Hartman]

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

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

i2c: validate user data in compat ioctl

Wrong user data may cause warning in i2c_transfer(), ex: zero msgs.
Userspace should not be able to trigger warnings, so this patch adds
validation checks for user data in compact ioctl to prevent reported
warnings

The Linux kernel CVE team has assigned CVE-2021-46934 to this issue.


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

	Issue introduced in 4.15 with commit 7d5cb45655f2 and fixed in 4.19.224 with commit 407c8708fb1b
	Issue introduced in 4.15 with commit 7d5cb45655f2 and fixed in 5.4.170 with commit 9e4a3f47eff4
	Issue introduced in 4.15 with commit 7d5cb45655f2 and fixed in 5.10.90 with commit 8d31cbab4c29
	Issue introduced in 4.15 with commit 7d5cb45655f2 and fixed in 5.15.13 with commit f68599581067
	Issue introduced in 4.15 with commit 7d5cb45655f2 and fixed in 5.16 with commit bb436283e25a

Please see https://www.kernel.org or 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-2021-46934
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/i2c/i2c-dev.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/407c8708fb1bf2d4afc5337ef50635cf540c364b
	https://git.kernel.org/stable/c/9e4a3f47eff476097e0c7faac04d1831fc70237d
	https://git.kernel.org/stable/c/8d31cbab4c295d7010ebb729e9d02d0e9cece18f
	https://git.kernel.org/stable/c/f68599581067e8a5a8901ba9eb270b4519690e26
	https://git.kernel.org/stable/c/bb436283e25aaf1533ce061605d23a9564447bdf