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>

1 files changed, 12 insertions, 3 deletions

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index db49ec4c748e..9fbbaa041a31 100644
--- 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