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

commit f01d35a15fa04162a58b95970fc01fa70ec9dacd upstream.

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...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[bwh: Backported to 3.2:
 - Adjust filename, context
 - Add kfree(priv->iv) to one additional failure path]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index 7138540..d00b3e3 100644 (file)
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -570,6 +570,7 @@ static ssize_t ep_aio_read_retry(struct kiocb *iocb)
                        break;
        }
        kfree(priv->buf);
                        break;
        }
        kfree(priv->buf);

+       kfree(priv->iv);

        kfree(priv);
        return len;
 }
        kfree(priv);
        return len;
 }


@@ -591,6 +592,7 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
         */
        if (priv->iv == NULL || unlikely(req->actual == 0)) {
                kfree(req->buf);
         */
        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 */
                kfree(priv);
                iocb->private = NULL;
                /* aio_complete() reports bytes-transferred _and_ faults */


@@ -626,7 +628,7 @@ ep_aio_rwtail(
        struct usb_request      *req;
        ssize_t                 value;
 
        struct usb_request      *req;
        ssize_t                 value;
 

-       priv = kmalloc(sizeof *priv, GFP_KERNEL);
+       priv = kzalloc(sizeof *priv, GFP_KERNEL);

        if (!priv) {
                value = -ENOMEM;
 fail:
        if (!priv) {
                value = -ENOMEM;
 fail:


@@ -634,7 +636,14 @@ fail:
                return value;
        }
        iocb->private = priv;
                return value;
        }
        iocb->private = priv;

-       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;
 
        value = get_ready_ep(iocb->ki_filp->f_flags, epdata);
        priv->nr_segs = nr_segs;
 
        value = get_ready_ep(iocb->ki_filp->f_flags, epdata);


@@ -672,6 +681,7 @@ fail:
        mutex_unlock(&epdata->lock);
 
        if (unlikely(value)) {
        mutex_unlock(&epdata->lock);
 
        if (unlikely(value)) {

+               kfree(priv->iv);

                kfree(priv);
                put_ep(epdata);
        } else
                kfree(priv);
                put_ep(epdata);
        } else