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

commit b348d7dddb6c4fbfc810b7a0626e8ec9e29f7cbb upstream.

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>
[bwh: Backported to 3.2: adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/staging/usbip/usbip_common.c b/drivers/staging/usbip/usbip_common.c
index 194e974..4fbef0c 100644 (file)
--- a/drivers/staging/usbip/usbip_common.c
+++ b/drivers/staging/usbip/usbip_common.c
@@ -820,6 +820,17 @@ int usbip_recv_xbuff(struct usbip_device *ud, struct urb *urb)
        if (!(size > 0))
                return 0;
 
        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_xmit(0, ud->tcp_socket, (char *)urb->transfer_buffer,
                         size, 0);
        if (ret != size) {
        ret = usbip_xmit(0, ud->tcp_socket, (char *)urb->transfer_buffer,
                         size, 0);
        if (ret != size) {