comedi: vmk80xx: fix transfer-buffer overflows

stable inclusion
from stable-5.10.79
commit 33d7a470730dfe7c9bfc8da84575cf2cedd60d00
bugzilla: 185793 https://gitee.com/openeuler/kernel/issues/I4K65C

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=33d7a470730dfe7c9bfc8da84575cf2cedd60d00

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

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: NJohan Hovold <johan@kernel.org>
Reviewed-by: NIan Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20211025114532.4599-4-johan@kernel.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NBin Li <huawei.libin@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/staging/comedi/drivers/vmk80xx.c

@@ -90,6 +90,8 @@ enum {
 #define IC3_VERSION		BIT(0)
 #define IC6_VERSION		BIT(1)
 
+#define MIN_BUF_SIZE		64
+
 enum vmk80xx_model {
 	VMK8055_MODEL,
 	VMK8061_MODEL
@@ -678,12 +680,12 @@ static int vmk80xx_alloc_usb_buffers(struct comedi_device *dev)
 	struct vmk80xx_private *devpriv = dev->private;
 	size_t size;
 
-	size = usb_endpoint_maxp(devpriv->ep_rx);
+	size = max(usb_endpoint_maxp(devpriv->ep_rx), MIN_BUF_SIZE);
 	devpriv->usb_rx_buf = kzalloc(size, GFP_KERNEL);
 	if (!devpriv->usb_rx_buf)
 		return -ENOMEM;
 
-	size = usb_endpoint_maxp(devpriv->ep_tx);
+	size = max(usb_endpoint_maxp(devpriv->ep_rx), MIN_BUF_SIZE);
 	devpriv->usb_tx_buf = kzalloc(size, GFP_KERNEL);
 	if (!devpriv->usb_tx_buf)
 		return -ENOMEM;