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

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>

Change-Id: I93342475b7e72ae44fed7d7c8f92d5f8dbf53c8a
This commit is contained in:
Yavuz, Tuba 2018-03-23 17:00:38 +00:00 committed by L R
parent 02c9e1032a
commit 628d00a9e1
1 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
drivers/usb/gadget/f_midi.c
View File

@ -214,7 +214,9 @@ static struct usb_request *midi_alloc_ep_req(struct usb_ep *ep, unsigned length)
static void midi_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);
}
@ -379,7 +381,8 @@ 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);
midi_free_ep_req(midi->out_ep, req);
if (req->buf != NULL)
midi_free_ep_req(midi->out_ep, req);
return err;
}
}