Subject: CVE-2021-47224: net: ll_temac: Make sure to free skb when it is completely used

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

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

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

net: ll_temac: Make sure to free skb when it is completely used

With the skb pointer piggy-backed on the TX BD, we have a simple and
efficient way to free the skb buffer when the frame has been transmitted.
But in order to avoid freeing the skb while there are still fragments from
the skb in use, we need to piggy-back on the TX BD of the skb, not the
first.

Without this, we are doing use-after-free on the DMA side, when the first
BD of a multi TX BD packet is seen as completed in xmit_done, and the
remaining BDs are still being processed.

The Linux kernel CVE team has assigned CVE-2021-47224 to this issue.

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

	Fixed in 5.4.128 with commit 6d120ab4dc39
	Fixed in 5.10.46 with commit 019ab7d044d0
	Fixed in 5.12.13 with commit e8afe05bd359
	Fixed in 5.13 with commit 6aa32217a9a4

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-2021-47224
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/ethernet/xilinx/ll_temac_main.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/6d120ab4dc39a543c6b63361e1d0541c382900a3
	https://git.kernel.org/stable/c/019ab7d044d0ebf97e1236bb8935b7809be92358
	https://git.kernel.org/stable/c/e8afe05bd359ebe12a61dbdc94c06c00ea3e8d4b
	https://git.kernel.org/stable/c/6aa32217a9a446275440ee8724b1ecaf1838df47