usb: gadget: f_hid: fix: Move IN request allocation to set_alt()

Since commit: ba1582f22231 ("usb: gadget: f_hid: use alloc_ep_req()")
we cannot allocate any requests in bind() as we check if we should
align request buffer based on endpoint descriptor which is assigned
in set_alt().

Allocating request in bind() function causes a NULL pointer
dereference.

This commit moves allocation of IN request from bind() to set_alt()
to prevent this issue.

Fixes: ba1582f22231 ("usb: gadget: f_hid: use alloc_ep_req()")
Cc: stable@vger.kernel.org
Tested-by: David Lechner <david@lechnology.com>
Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_hid.c

@@ -338,6 +338,7 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
 			    size_t count, loff_t *offp)
 {
 	struct f_hidg *hidg  = file->private_data;
+	struct usb_request *req;
 	unsigned long flags;
 	ssize_t status = -ENOMEM;
 
@@ -347,7 +348,7 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
 	spin_lock_irqsave(&hidg->write_spinlock, flags);
 
 #define WRITE_COND (!hidg->write_pending)
-
+try_again:
 	/* write queue */
 	while (!WRITE_COND) {
 		spin_unlock_irqrestore(&hidg->write_spinlock, flags);
@@ -362,6 +363,7 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
 	}
 
 	hidg->write_pending = 1;
+	req = hidg->req;
 	count  = min_t(unsigned, count, hidg->report_length);
 
 	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
@@ -374,24 +376,38 @@ static ssize_t f_hidg_write(struct file *file, const char __user *buffer,
 		goto release_write_pending;
 	}
 
-	hidg->req->status   = 0;
-	hidg->req->zero     = 0;
-	hidg->req->length   = count;
-	hidg->req->complete = f_hidg_req_complete;
-	hidg->req->context  = hidg;
+	spin_lock_irqsave(&hidg->write_spinlock, flags);
+
+	/* we our function has been disabled by host */
+	if (!hidg->req) {
+		free_ep_req(hidg->in_ep, hidg->req);
+		/*
+		 * TODO
+		 * Should we fail with error here?
+		 */
+		goto try_again;
+	}
+
+	req->status   = 0;
+	req->zero     = 0;
+	req->length   = count;
+	req->complete = f_hidg_req_complete;
+	req->context  = hidg;
 
 	status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
 	if (status < 0) {
 		ERROR(hidg->func.config->cdev,
 			"usb_ep_queue error on int endpoint %zd\n", status);
-		goto release_write_pending;
+		goto release_write_pending_unlocked;
 	} else {
 		status = count;
 	}
+	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
 
 	return status;
 release_write_pending:
 	spin_lock_irqsave(&hidg->write_spinlock, flags);
+release_write_pending_unlocked:
 	hidg->write_pending = 0;
 	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
 
@@ -595,12 +611,23 @@ static void hidg_disable(struct usb_function *f)
 		kfree(list);
 	}
 	spin_unlock_irqrestore(&hidg->read_spinlock, flags);
+
+	spin_lock_irqsave(&hidg->write_spinlock, flags);
+	if (!hidg->write_pending) {
+		free_ep_req(hidg->in_ep, hidg->req);
+		hidg->write_pending = 1;
+	}
+
+	hidg->req = NULL;
+	spin_unlock_irqrestore(&hidg->write_spinlock, flags);
 }
 
 static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 {
 	struct usb_composite_dev		*cdev = f->config->cdev;
 	struct f_hidg				*hidg = func_to_hidg(f);
+	struct usb_request			*req_in = NULL;
+	unsigned long				flags;
 	int i, status = 0;
 
 	VDBG(cdev, "hidg_set_alt intf:%d alt:%d\n", intf, alt);
@@ -621,6 +648,12 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 			goto fail;
 		}
 		hidg->in_ep->driver_data = hidg;
+
+		req_in = hidg_alloc_ep_req(hidg->in_ep, hidg->report_length);
+		if (!req_in) {
+			status = -ENOMEM;
+			goto disable_ep_in;
+		}
 	}
 
 
@@ -632,12 +665,12 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 					    hidg->out_ep);
 		if (status) {
 			ERROR(cdev, "config_ep_by_speed FAILED!\n");
-			goto fail;
+			goto free_req_in;
 		}
 		status = usb_ep_enable(hidg->out_ep);
 		if (status < 0) {
 			ERROR(cdev, "Enable OUT endpoint FAILED!\n");
-			goto fail;
+			goto free_req_in;
 		}
 		hidg->out_ep->driver_data = hidg;
 
@@ -653,17 +686,37 @@ static int hidg_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 				req->context  = hidg;
 				status = usb_ep_queue(hidg->out_ep, req,
 						      GFP_ATOMIC);
-				if (status)
+				if (status) {
 					ERROR(cdev, "%s queue req --> %d\n",
 						hidg->out_ep->name, status);
+					free_ep_req(hidg->out_ep, req);
+				}
 			} else {
-				usb_ep_disable(hidg->out_ep);
 				status = -ENOMEM;
-				goto fail;
+				goto disable_out_ep;
 			}
 		}
 	}
 
+	if (hidg->in_ep != NULL) {
+		spin_lock_irqsave(&hidg->write_spinlock, flags);
+		hidg->req = req_in;
+		hidg->write_pending = 0;
+		spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+
+		wake_up(&hidg->write_queue);
+	}
+	return 0;
+disable_out_ep:
+	usb_ep_disable(hidg->out_ep);
+free_req_in:
+	if (req_in)
+		free_ep_req(hidg->in_ep, req_in);
+
+disable_ep_in:
+	if (hidg->in_ep)
+		usb_ep_disable(hidg->in_ep);
+
 fail:
 	return status;
 }
@@ -712,12 +765,6 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 		goto fail;
 	hidg->out_ep = ep;
 
-	/* preallocate request and buffer */
-	status = -ENOMEM;
-	hidg->req = alloc_ep_req(hidg->in_ep, hidg->report_length);
-	if (!hidg->req)
-		goto fail;
-
 	/* set descriptor dynamic values */
 	hidg_interface_desc.bInterfaceSubClass = hidg->bInterfaceSubClass;
 	hidg_interface_desc.bInterfaceProtocol = hidg->bInterfaceProtocol;
@@ -755,6 +802,8 @@ static int hidg_bind(struct usb_configuration *c, struct usb_function *f)
 		goto fail;
 
 	spin_lock_init(&hidg->write_spinlock);
+	hidg->write_pending = 1;
+	hidg->req = NULL;
 	spin_lock_init(&hidg->read_spinlock);
 	init_waitqueue_head(&hidg->write_queue);
 	init_waitqueue_head(&hidg->read_queue);
@@ -1019,10 +1068,6 @@ static void hidg_unbind(struct usb_configuration *c, struct usb_function *f)
 	device_destroy(hidg_class, MKDEV(major, hidg->minor));
 	cdev_del(&hidg->cdev);
 
-	/* disable/free request and end point */
-	usb_ep_disable(hidg->in_ep);
-	free_ep_req(hidg->in_ep, hidg->req);
-
 	usb_free_all_descriptors(f);
 }