Subject: CVE-2021-47367: virtio-net: fix pages leaking when building skb in big mode

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

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

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

virtio-net: fix pages leaking when building skb in big mode

We try to use build_skb() if we had sufficient tailroom. But we forget
to release the unused pages chained via private in big mode which will
leak pages. Fixing this by release the pages after building the skb in
big mode.

The Linux kernel CVE team has assigned CVE-2021-47367 to this issue.

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

	Issue introduced in 5.13 with commit fb32856b16ad and fixed in 5.14.9 with commit f020bb63b5d2
	Issue introduced in 5.13 with commit fb32856b16ad and fixed in 5.15 with commit afd92d82c9d7

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-2021-47367
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/net/virtio_net.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/f020bb63b5d2e5576acadd10e158fe3b04af67ba
	https://git.kernel.org/stable/c/afd92d82c9d715fb97565408755acad81573591a