From: "Yavuz, Tuba" tuba@ece.ufl.edu

cherry pick from commit 7fafcfdf6377b18b2a726ea554d6e593ba44349f ("USB: gadget: f_midi: fixing a possible double-free in f_midi") Removing 'return err;' from conflict.

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 # 4.4.y --- drivers/usb/gadget/function/f_midi.c | 3 ++- drivers/usb/gadget/u_f.h | 2 ++ 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/function/f_midi.c b/drivers/usb/gadget/function/f_midi.c index 5ead414586a1..e5c4a907e5d4 100644 --- a/drivers/usb/gadget/function/f_midi.c +++ b/drivers/usb/gadget/function/f_midi.c @@ -366,7 +366,8 @@ static int f_midi_set_alt(struct usb_function *f, unsigned intf, unsigned alt) if (err) { ERROR(midi, "%s queue req: %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); } }

diff --git a/drivers/usb/gadget/u_f.h b/drivers/usb/gadget/u_f.h index 69a1d10df04f..3ee365fbc2e2 100644 --- a/drivers/usb/gadget/u_f.h +++ b/drivers/usb/gadget/u_f.h @@ -65,7 +65,9 @@ struct usb_request *alloc_ep_req(struct usb_ep *ep, size_t len, int default_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); }