Subject: CVE-2021-47231: can: mcba_usb: fix memory leak in mcba_usb

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

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

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

can: mcba_usb: fix memory leak in mcba_usb

Syzbot reported memory leak in SocketCAN driver for Microchip CAN BUS
Analyzer Tool. The problem was in unfreed usb_coherent.

In mcba_usb_start() 20 coherent buffers are allocated and there is
nothing, that frees them:

1) In callback function the urb is resubmitted and that's all
2) In disconnect function urbs are simply killed, but URB_FREE_BUFFER
   is not set (see mcba_usb_start) and this flag cannot be used with
   coherent buffers.

Fail log:
| [ 1354.053291][ T8413] mcba_usb 1-1:0.0 can0: device disconnected
| [ 1367.059384][ T8420] kmemleak: 20 new suspected memory leaks (see /sys/kernel/debug/kmem)

So, all allocated buffers should be freed with usb_free_coherent()
explicitly

NOTE:
The same pattern for allocating and freeing coherent buffers
is used in drivers/net/can/usb/kvaser_usb/kvaser_usb_core.c

The Linux kernel CVE team has assigned CVE-2021-47231 to this issue.

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

	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 4.14.238 with commit 89df95ce32be
	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 4.19.196 with commit a115198caaab
	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 5.4.128 with commit 6f87c0e21ad2
	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 5.10.46 with commit 6bd3d80d1f01
	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 5.12.13 with commit d0760a4ef856
	Issue introduced in 4.12 with commit 51f3baad7de9 and fixed in 5.13 with commit 91c02557174b

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-2021-47231
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/usb/mcba_usb.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/89df95ce32be204eef2e7d4b2f6fb552fb191a68
	https://git.kernel.org/stable/c/a115198caaab6d663bef75823a3c5f0802306d60
	https://git.kernel.org/stable/c/6f87c0e21ad20dd3d22108e33db1c552dfa352a0
	https://git.kernel.org/stable/c/6bd3d80d1f019cefa7011056c54b323f1d8b8e83
	https://git.kernel.org/stable/c/d0760a4ef85697bc756d06eae17ae27f3f055401
	https://git.kernel.org/stable/c/91c02557174be7f72e46ed7311e3bea1939840b0