USB: gadget: f_midi: fixing a possible double-free in f_midi

commit 7fafcfdf6377b18b2a726ea554d6e593ba44349f upstream.

It looks like there is a possibility of a double-free vulnerability on an
error path of the f_midi_set_alt function in the f_midi driver. If the
path is feasible then free_ep_req gets called twice:

         req->complete = f_midi_complete;
         err = usb_ep_queue(midi->out_ep, req, GFP_ATOMIC);
            => ...
             usb_gadget_giveback_request
               =>
                 f_midi_complete (CALLBACK)
                   (inside f_midi_complete, for various cases of status)
                   free_ep_req(ep, req); // first kfree
         if (err) {
                 ERROR(midi, "%s: couldn't enqueue request: %d\n",
                             midi->out_ep->name, err);
                 free_ep_req(midi->out_ep, req); // second kfree
                 return err;
         }

The double-free possibility was introduced with commit ad0d1a058eac
("usb: gadget: f_midi: fix leak on failed to enqueue out requests").

Found by MOXCAFE tool.

Signed-off-by: Tuba Yavuz <tuba@ece.ufl.edu>
Fixes: ad0d1a058eac ("usb: gadget: f_midi: fix leak on failed to enqueue out requests")
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c
index 5d3d7941d2c2227f5ae9d9f219d34bfd0156665f..71cf552b8828122a4827fb3a888eb137fc0f7c43 100644 (file)
--- a/drivers/usb/gadget/function/f_midi.c
+++ b/drivers/usb/gadget/function/f_midi.c
@@ -405,7 +405,8 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
                if (err) {
                        ERROR(midi, "%s: couldn't enqueue request: %d\n",
                                    midi->out_ep->name, err);
-                       free_ep_req(midi->out_ep, req);
+                       if (req->buf != NULL)
+                               free_ep_req(midi->out_ep, req);
                        return err;
                }
        }

diff --git a/drivers/usb/gadget/u_f.h b/drivers/usb/gadget/u_f.h
index 7d53a4773d1af5a303e292234239769b97878d2f..2f03334c68741fc1bedcb4590fc61ff2d456db62 100644 (file)
--- a/drivers/usb/gadget/u_f.h
+++ b/drivers/usb/gadget/u_f.h
@@ -64,7 +64,9 @@ struct usb_request *alloc_ep_req(struct usb_ep *ep, size_t len);
 /* Frees a usb_request previously allocated by alloc_ep_req() */
 static inline void free_ep_req(struct usb_ep *ep, struct usb_request *req)
 {
+       WARN_ON(req->buf == NULL);
        kfree(req->buf);
+       req->buf = NULL;
        usb_ep_free_request(ep, req);
 }