Subject: CVE-2021-47519: can: m_can: m_can_read_fifo: fix memory leak in error branch

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

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

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

can: m_can: m_can_read_fifo: fix memory leak in error branch

In m_can_read_fifo(), if the second call to m_can_fifo_read() fails,
the function jump to the out_fail label and returns without calling
m_can_receive_skb(). This means that the skb previously allocated by
alloc_can_skb() is not freed. In other terms, this is a memory leak.

This patch adds a goto label to destroy the skb if an error occurs.

Issue was found with GCC -fanalyzer, please follow the link below for
details.

The Linux kernel CVE team has assigned CVE-2021-47519 to this issue.

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

	Issue introduced in 5.15 with commit e39381770ec9 and fixed in 5.15.8 with commit 75a422165477
	Issue introduced in 5.15 with commit e39381770ec9 and fixed in 5.16 with commit 31cb32a590d6

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-2021-47519
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/can/m_can/m_can.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/75a422165477dd12d2d20aa7c9ee7c9a281c9908
	https://git.kernel.org/stable/c/31cb32a590d62b18f69a9a6d433f4e69c74fdd56