staging: ozwpan: prevent a couple of underflows

The underflow in OZ_DATA_F_ISOC_FIXED seems not harmful, but this patch
is a clean up and makes my static checker a bit happier.

The underflow in OZ_VENDOR_CLASS_RSP seems like it could result in
memory corruption.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/ozwpan/ozusbsvc1.c b/drivers/staging/ozwpan/ozusbsvc1.c
index f660bb1..301fee8 100644 (file)
--- a/drivers/staging/ozwpan/ozusbsvc1.c
+++ b/drivers/staging/ozwpan/ozusbsvc1.c
@@ -342,12 +342,16 @@ static void oz_usb_handle_ep_data(struct oz_usb_ctx *usb_ctx,
        case OZ_DATA_F_ISOC_FIXED: {
                        struct oz_isoc_fixed *body =
                                (struct oz_isoc_fixed *)data_hdr;
-                       int data_len = len-sizeof(struct oz_isoc_fixed)+1;
+                       int data_len;
                        int unit_size = body->unit_size;
                        u8 *data = body->data;
                        int count;
                        int i;
 
+                       if (len < sizeof(struct oz_isoc_fixed) - 1)
+                               break;
+                       data_len = len - (sizeof(struct oz_isoc_fixed) - 1);
+
                        if (!unit_size)
                                break;
                        count = data_len/unit_size;
@@ -427,6 +431,11 @@ void oz_usb_rx(struct oz_pd *pd, struct oz_elt *elt)
        case OZ_VENDOR_CLASS_RSP: {
                        struct oz_vendor_class_rsp *body =
                                (struct oz_vendor_class_rsp *)usb_hdr;
+
+                       if (elt->length <
+                           sizeof(struct oz_vendor_class_rsp) - 1)
+                               break;
+
                        oz_hcd_control_cnf(usb_ctx->hport, body->req_id,
                                body->rcode, body->data, elt->length-
                                sizeof(struct oz_vendor_class_rsp)+1);