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Subject[PATCH 4.9 019/116] usb: gadget: f_ncm: Use atomic_t to track in-flight request
Date
From: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

commit 5b24c28cfe136597dc3913e1c00b119307a20c7e upstream.

Currently ncm->notify_req is used to flag when a request is in-flight.
ncm->notify_req is set to NULL and when a request completes it is
subsequently reset.

This is fundamentally buggy in that the unbind logic of the NCM driver will
unconditionally free ncm->notify_req leading to a NULL pointer dereference.

Fixes: 40d133d7f542 ("usb: gadget: f_ncm: convert to new function interface with backward compatibility")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/gadget/function/f_ncm.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)

--- a/drivers/usb/gadget/function/f_ncm.c
+++ b/drivers/usb/gadget/function/f_ncm.c
@@ -57,6 +57,7 @@ struct f_ncm {
struct usb_ep *notify;
struct usb_request *notify_req;
u8 notify_state;
+ atomic_t notify_count;
bool is_open;

const struct ndp_parser_opts *parser_opts;
@@ -552,7 +553,7 @@ static void ncm_do_notify(struct f_ncm *
int status;

/* notification already in flight? */
- if (!req)
+ if (atomic_read(&ncm->notify_count))
return;

event = req->buf;
@@ -592,7 +593,8 @@ static void ncm_do_notify(struct f_ncm *
event->bmRequestType = 0xA1;
event->wIndex = cpu_to_le16(ncm->ctrl_id);

- ncm->notify_req = NULL;
+ atomic_inc(&ncm->notify_count);
+
/*
* In double buffering if there is a space in FIFO,
* completion callback can be called right after the call,
@@ -602,7 +604,7 @@ static void ncm_do_notify(struct f_ncm *
status = usb_ep_queue(ncm->notify, req, GFP_ATOMIC);
spin_lock(&ncm->lock);
if (status < 0) {
- ncm->notify_req = req;
+ atomic_dec(&ncm->notify_count);
DBG(cdev, "notify --> %d\n", status);
}
}
@@ -637,17 +639,19 @@ static void ncm_notify_complete(struct u
case 0:
VDBG(cdev, "Notification %02x sent\n",
event->bNotificationType);
+ atomic_dec(&ncm->notify_count);
break;
case -ECONNRESET:
case -ESHUTDOWN:
+ atomic_set(&ncm->notify_count, 0);
ncm->notify_state = NCM_NOTIFY_NONE;
break;
default:
DBG(cdev, "event %02x --> %d\n",
event->bNotificationType, req->status);
+ atomic_dec(&ncm->notify_count);
break;
}
- ncm->notify_req = req;
ncm_do_notify(ncm);
spin_unlock(&ncm->lock);
}
@@ -1639,6 +1643,11 @@ static void ncm_unbind(struct usb_config
ncm_string_defs[0].id = 0;
usb_free_all_descriptors(f);

+ if (atomic_read(&ncm->notify_count)) {
+ usb_ep_dequeue(ncm->notify, ncm->notify_req);
+ atomic_set(&ncm->notify_count, 0);
+ }
+
kfree(ncm->notify_req->buf);
usb_ep_free_request(ncm->notify, ncm->notify_req);
}

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