CVE-2021-47159: net: dsa: fix a crash if ->get_sset_count() fails

CVE-2021-47159: net: dsa: fix a crash if ->get_sset_count() fails

[Greg Kroah-Hartman]

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

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

net: dsa: fix a crash if ->get_sset_count() fails

If ds->ops->get_sset_count() fails then it "count" is a negative error
code such as -EOPNOTSUPP.  Because "i" is an unsigned int, the negative
error code is type promoted to a very high value and the loop will
corrupt memory until the system crashes.

Fix this by checking for error codes and changing the type of "i" to
just int.

The Linux kernel CVE team has assigned CVE-2021-47159 to this issue.


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

	Issue introduced in 4.7 with commit badf3ada60ab and fixed in 4.19.193 with commit 0f2cb08c57ed
	Issue introduced in 4.7 with commit badf3ada60ab and fixed in 5.4.124 with commit ce5355f140a7
	Issue introduced in 4.7 with commit badf3ada60ab and fixed in 5.10.42 with commit caff86f85512
	Issue introduced in 4.7 with commit badf3ada60ab and fixed in 5.12.9 with commit 7b22466648a4
	Issue introduced in 4.7 with commit badf3ada60ab and fixed in 5.13 with commit a269333fa5c0

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-2021-47159
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:
	net/dsa/master.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/0f2cb08c57edefb0e7b5045e0e3e9980a3d3aa37
	https://git.kernel.org/stable/c/ce5355f140a7987011388c7e30c4f8fbe180d3e8
	https://git.kernel.org/stable/c/caff86f85512b8e0d9830e8b8b0dfe13c68ce5b6
	https://git.kernel.org/stable/c/7b22466648a4f8e3e94f57ca428d1531866d1373
	https://git.kernel.org/stable/c/a269333fa5c0c8e53c92b5a28a6076a28cde3e83