[PATCH v4] usb: gadget: eem: fix echo command packet response issue

[Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>]

From: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>

when receive eem echo command, it will send a response,
but queue this response to the usb request which allocate
from gadget device endpoint zero,
and transmit the request to IN endpoint of eem interface.

on dwc3 gadget, it will trigger following warning in function
__dwc3_gadget_ep_queue(),

	if (WARN(req->dep != dep, "request %pK belongs to '%s'\n",
				&req->request, req->dep->name))
		return -EINVAL;

fix it by allocating a usb request from IN endpoint of eem interface,
and transmit the usb request to same IN endpoint of eem interface.

Fixes: 9b39e9ddedee ("USB: gadget: Add EEM gadget driver")
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Linyu Yuan <linyyuan@xxxxxxxxxxxxxx>
---

v4: add Fixes tags and cc stable
v3: use exist goto label 'next'
v2: fix mail format and expand commit message

 drivers/usb/gadget/function/f_eem.c | 43 ++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/gadget/function/f_eem.c b/drivers/usb/gadget/function/f_eem.c
index 2cd9942707b4..5d38f29bda72 100644
--- a/drivers/usb/gadget/function/f_eem.c
+++ b/drivers/usb/gadget/function/f_eem.c
@@ -30,6 +30,11 @@ struct f_eem {
 	u8				ctrl_id;
 };
 
+struct in_context {
+	struct sk_buff	*skb;
+	struct usb_ep	*ep;
+};
+
 static inline struct f_eem *func_to_eem(struct usb_function *f)
 {
 	return container_of(f, struct f_eem, port.func);
@@ -320,9 +325,12 @@ static int eem_bind(struct usb_configuration *c, struct usb_function *f)
 
 static void eem_cmd_complete(struct usb_ep *ep, struct usb_request *req)
 {
-	struct sk_buff *skb = (struct sk_buff *)req->context;
+	struct in_context *ctx = req->context;
 
-	dev_kfree_skb_any(skb);
+	dev_kfree_skb_any(ctx->skb);
+	kfree(req->buf);
+	usb_ep_free_request(ctx->ep, req);
+	kfree(ctx);
 }
 
 /*
@@ -410,7 +418,9 @@ static int eem_unwrap(struct gether *port,
 		 * b15:		bmType (0 == data, 1 == command)
 		 */
 		if (header & BIT(15)) {
-			struct usb_request	*req = cdev->req;
+			struct usb_request	*req;
+			struct in_context	*ctx;
+			struct usb_ep		*ep;
 			u16			bmEEMCmd;
 
 			/* EEM command packet format:
@@ -439,11 +449,36 @@ static int eem_unwrap(struct gether *port,
 				skb_trim(skb2, len);
 				put_unaligned_le16(BIT(15) | BIT(11) | len,
 							skb_push(skb2, 2));
+
+				ep = port->in_ep;
+				req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+				if (!req) {
+					dev_kfree_skb_any(skb2);
+					goto next;
+				}
+
+				req->buf = kmalloc(skb2->len, GFP_KERNEL);
+				if (!req->buf) {
+					usb_ep_free_request(ep, req);
+					dev_kfree_skb_any(skb2);
+					goto next;
+				}
+
+				ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
+				if (!ctx) {
+					kfree(req->buf);
+					usb_ep_free_request(ep, req);
+					dev_kfree_skb_any(skb2);
+					goto next;
+				}
+				ctx->skb = skb2;
+				ctx->ep = ep;
+
 				skb_copy_bits(skb2, 0, req->buf, skb2->len);
 				req->length = skb2->len;
 				req->complete = eem_cmd_complete;
 				req->zero = 1;
-				req->context = skb2;
+				req->context = ctx;
 				if (usb_ep_queue(port->in_ep, req, GFP_ATOMIC))
 					DBG(cdev, "echo response queue fail\n");
 				break;
-- 
2.25.1