Commit 57999d11 authored Sep 22, 2017 by Dan Carpenter Committed by Greg Kroah-Hartman Sep 25, 2017

USB: devio: Prevent integer overflow in proc_do_submiturb()



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.

Fixes: 1129d270 ("USB: Increase usbfs transfer limit")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 1fbbb78f

drivers/usb/core/devio.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -140,6 +140,9 @@ 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 */
		@@ -1460,6 +1463,8 @@ static int proc_do_submiturb(struct usb_dev_state ps, struct usbdevfs_urb uurb
		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 &&

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