[lkml]   [2019]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
SubjectUSB: gadget: f_midi: fixing a possible double-free in f_midi
From: "Yavuz, Tuba" <>

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);
=> ...
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 <>
Fixes: ad0d1a058eac ("usb: gadget: f_midi: fix leak on failed to enqueue out requests")
Acked-by: Felipe Balbi <>
Cc: stable <> # 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);
+ req->buf = NULL;
usb_ep_free_request(ep, req);

 \ /
  Last update: 2019-08-20 19:55    [W:0.053 / U:4.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site