Subject: CVE-2021-47475: comedi: vmk80xx: fix transfer-buffer overflows

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

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

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

comedi: vmk80xx: fix transfer-buffer overflows

The driver uses endpoint-sized USB transfer buffers but up until
recently had no sanity checks on the sizes.

Commit e1f13c879a7c ("staging: comedi: check validity of wMaxPacketSize
of usb endpoints found") inadvertently fixed NULL-pointer dereferences
when accessing the transfer buffers in case a malicious device has a
zero wMaxPacketSize.

Make sure to allocate buffers large enough to handle also the other
accesses that are done without a size check (e.g. byte 18 in
vmk80xx_cnt_insn_read() for the VMK8061_MODEL) to avoid writing beyond
the buffers, for example, when doing descriptor fuzzing.

The original driver was for a low-speed device with 8-byte buffers.
Support was later added for a device that uses bulk transfers and is
presumably a full-speed device with a maximum 64-byte wMaxPacketSize.

The Linux kernel CVE team has assigned CVE-2021-47475 to this issue.

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

	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 4.4.292 with commit 5229159f1d05
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 4.9.290 with commit ec85bcff4ed0
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 4.14.255 with commit 40d2a7e278e2
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 4.19.217 with commit 7a2021b896de
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 5.4.159 with commit 199acd8c110e
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 5.10.79 with commit 33d7a470730d
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 5.14.18 with commit 278484ae9329
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 5.15.2 with commit 06ac746d57e6
	Issue introduced in 2.6.31 with commit 985cafccbf9b and fixed in 5.16 with commit a23461c47482

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-2021-47475
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/comedi/drivers/vmk80xx.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/5229159f1d052821007aff1a1beb7873eacf1a9f
	https://git.kernel.org/stable/c/ec85bcff4ed09260243d8f39faba99e1041718ba
	https://git.kernel.org/stable/c/40d2a7e278e2e7c0a5fd7e997e7eb63945bf93f7
	https://git.kernel.org/stable/c/7a2021b896de1ad559d33b5c5cdd20b982242088
	https://git.kernel.org/stable/c/199acd8c110e3ae62833c24f632b0bb1c9f012a9
	https://git.kernel.org/stable/c/33d7a470730dfe7c9bfc8da84575cf2cedd60d00
	https://git.kernel.org/stable/c/278484ae93297b1bb1ce755f9d3b6d95a48c7d47
	https://git.kernel.org/stable/c/06ac746d57e6d32b062e220415c607b7e2e0fa50
	https://git.kernel.org/stable/c/a23461c47482fc232ffc9b819539d1f837adf2b1