USB: usbip: fix potential out-of-bounds write

Fix potential out-of-bounds write to urb->transfer_buffer
usbip handles network communication directly in the kernel. When receiving a
packet from its peer, usbip code parses headers according to protocol. As
part of this parsing urb->actual_length is filled. Since the input for
urb->actual_length comes from the network, it should be treated as untrusted.
Any entity controlling the network may put any value in the input and the
preallocated urb->transfer_buffer may not be large enough to hold the data.
Thus, the malicious entity is able to write arbitrary data to kernel memory.

Signed-off-by: Ignat Korchagin <ignat.korchagin@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/usb/usbip/usbip_common.c b/drivers/usb/usbip/usbip_common.c
index facaaf003f19..e40da7759a0e 100644
--- a/drivers/usb/usbip/usbip_common.c
+++ b/drivers/usb/usbip/usbip_common.c
@@ -741,6 +741,17 @@ int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
         if (!(size > 0))
                 return 0;
 
+        if (size > urb->transfer_buffer_length) {
+                /* should not happen, probably malicious packet */
+                if (ud->side == USBIP_STUB) {
+                        usbip_event_add(ud, SDEV_EVENT_ERROR_TCP);
+                        return 0;
+                } else {
+                        usbip_event_add(ud, VDEV_EVENT_ERROR_TCP);
+                        return -EPIPE;
+                }
+        }
+
         ret = usbip_recv(ud->tcp_socket, urb->transfer_buffer, size);
         if (ret != size) {
                 dev_err(&urb->dev->dev, "recv xbuf, %d\n", ret);