gadgetfs: use-after-free in ->aio_read()

AIO_PREAD requests call ->aio_read() with iovec on caller's stack, so if
we are going to access it asynchronously, we'd better get ourselves
a copy - the one on kernel stack of aio_run_iocb() won't be there
anymore.  function/f_fs.c take care of doing that, legacy/inode.c
doesn't...

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index db49ec4c748e9469bd694645c8cfc22df7c829fa..9fbbaa041a3106adcc8b33a34a9e7412048610ff 100644 (file)
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -566,7 +566,6 @@ static ssize_t ep_copy_to_user(struct kiocb_priv *priv)
                if (total == 0)
                        break;
        }
-
        return len;
 }
 
@@ -585,6 +584,7 @@ static void ep_user_copy_worker(struct work_struct *work)
        aio_complete(iocb, ret, ret);
 
        kfree(priv->buf);
+       kfree(priv->iv);
        kfree(priv);
 }
 
@@ -605,6 +605,7 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
         */
        if (priv->iv == NULL || unlikely(req->actual == 0)) {
                kfree(req->buf);
+               kfree(priv->iv);
                kfree(priv);
                iocb->private = NULL;
                /* aio_complete() reports bytes-transferred _and_ faults */
@@ -640,7 +641,7 @@ ep_aio_rwtail(
        struct usb_request      *req;
        ssize_t                 value;
 
-       priv = kmalloc(sizeof *priv, GFP_KERNEL);
+       priv = kzalloc(sizeof *priv, GFP_KERNEL);
        if (!priv) {
                value = -ENOMEM;
 fail:
@@ -649,7 +650,14 @@ fail:
        }
        iocb->private = priv;
        priv->iocb = iocb;
-       priv->iv = iv;
+       if (iv) {
+               priv->iv = kmemdup(iv, nr_segs * sizeof(struct iovec),
+                                  GFP_KERNEL);
+               if (!priv->iv) {
+                       kfree(priv);
+                       goto fail;
+               }
+       }
        priv->nr_segs = nr_segs;
        INIT_WORK(&priv->work, ep_user_copy_worker);
 
@@ -689,6 +697,7 @@ fail:
        mutex_unlock(&epdata->lock);
 
        if (unlikely(value)) {
+               kfree(priv->iv);
                kfree(priv);
                put_ep(epdata);
        } else