Patch "USB: devio: Prevent integer overflow in proc_do_submiturb()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

USB: devio: Prevent integer overflow in proc_do_submiturb()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-devio-prevent-integer-overflow-in-proc_do_submiturb.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Dan Carpenter <[email protected]>
Date: Fri, 22 Sep 2017 23:43:25 +0300
Subject: USB: devio: Prevent integer overflow in proc_do_submiturb()

From: Dan Carpenter <[email protected]>

commit 57999d1107c1e60c2ca7088f2ac0f819e2f554b3 upstream.

There used to be an integer overflow check in proc_do_submiturb() but we removed it. It turns out that it's still required. The uurb->buffer_length variable is a signed integer and it's controlled by the user. It can lead to an integer overflow when we do:

	num_sgs = DIV_ROUND_UP(uurb->buffer_length, USB_SG_SIZE);

If we strip away the macro then that line looks like this:

	num_sgs = (uurb->buffer_length + USB_SG_SIZE - 1) / USB_SG_SIZE;
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

It's the first addition which can overflow.

---
 drivers/usb/core/devio.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -118,6 +118,9 @@ module_param(usbfs_memory_mb, uint, 0644
 MODULE_PARM_DESC(usbfs_memory_mb,
 		"maximum MB allowed for usbfs buffers (0 = no limit)");
 
+/* Hard limit, necessary to avoid arithmetic overflow */
+#define USBFS_XFER_MAX         (UINT_MAX / 2 - 1000000)
+
 static atomic64_t usbfs_memory_usage;	/* Total memory currently allocated */
 
 /* Check whether it's okay to allocate more memory for a transfer */

@@ -1298,6 +1301,8 @@ static int proc_do_submiturb(struct usb_
 				USBDEVFS_URB_ZERO_PACKET |
 				USBDEVFS_URB_NO_INTERRUPT))
 		return -EINVAL;
+	if ((unsigned int)uurb->buffer_length >= USBFS_XFER_MAX)
+		return -EINVAL;
 	if (uurb->buffer_length > 0 && !uurb->buffer)
 		return -EINVAL;
 	if (!(uurb->type == USBDEVFS_URB_TYPE_CONTROL &&

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/usb-devio-prevent-integer-overflow-in-proc_do_submiturb.patch