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Subject[PATCH 3.2 082/115] USB: usbip: fix potential out-of-bounds write
3.2.80-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Ignat Korchagin <ignat.korchagin@gmail.com>

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>
---
drivers/staging/usbip/usbip_common.c | 11 +++++++++++
1 file changed, 11 insertions(+)

--- 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
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) {
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