comedi: vmk80xx: fix transfer-buffer overflows

stable inclusion
from stable-v4.19.217
commit 7a2021b896de1ad559d33b5c5cdd20b982242088
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9RD17
CVE: CVE-2021-47475

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7a2021b896de1ad559d33b5c5cdd20b982242088



--------------------------------

commit a23461c4 upstream.

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

Commit e1f13c87 ("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.

Fixes: 985cafcc ("Staging: Comedi: vmk80xx: Add k8061 support")
Cc: stable@vger.kernel.org      # 2.6.31
Signed-off-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211025114532.4599-4-johan@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Cai Xinchen <caixinchen1@huawei.com>