linux-kernel - [PATCH 3/3] usb: gadget: f_hid: tidy error handling in hidg

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Message-Id: <20221122123523.3068034-4-john@metanate.com>
Date:   Tue, 22 Nov 2022 12:35:23 +0000
From:   John Keeping <john@...anate.com>
To:     linux-usb@...r.kernel.org
Cc:     Fabien Chouteau <fabien.chouteau@...co.com>,
        Peter Korsgaard <peter.korsgaard@...co.com>,
        Felipe Balbi <balbi@...com>,
        Andrzej Pietrasiewicz <andrzej.p@...sung.com>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        John Keeping <john@...anate.com>, Lee Jones <lee@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH 3/3] usb: gadget: f_hid: tidy error handling in hidg_alloc

Unify error handling at the end of the function, reducing the risk of
missing something on one of the error paths.

Moving the increment of opts->refcnt later means there is no need to
decrement it on the error path and is safe as this is guarded by
opts->lock which is held for this entire section.

Signed-off-by: John Keeping <john@...anate.com>
---
 drivers/usb/gadget/function/f_hid.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/gadget/function/f_hid.c b/drivers/usb/gadget/function/f_hid.c
index 6be6009f911e..a8da3b4a2855 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -1269,18 +1269,14 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 	opts = container_of(fi, struct f_hid_opts, func_inst);
 
 	mutex_lock(&opts->lock);
-	++opts->refcnt;
 
 	device_initialize(&hidg->dev);
 	hidg->dev.release = hidg_release;
 	hidg->dev.class = hidg_class;
 	hidg->dev.devt = MKDEV(major, opts->minor);
 	ret = dev_set_name(&hidg->dev, "hidg%d", opts->minor);
-	if (ret) {
-		--opts->refcnt;
-		mutex_unlock(&opts->lock);
-		return ERR_PTR(ret);
-	}
+	if (ret)
+		goto err_unlock;
 
 	hidg->bInterfaceSubClass = opts->subclass;
 	hidg->bInterfaceProtocol = opts->protocol;
@@ -1291,14 +1287,13 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 						 opts->report_desc_length,
 						 GFP_KERNEL);
 		if (!hidg->report_desc) {
-			put_device(&hidg->dev);
-			--opts->refcnt;
-			mutex_unlock(&opts->lock);
-			return ERR_PTR(-ENOMEM);
+			ret = -ENOMEM;
+			goto err_put_device;
 		}
 	}
 	hidg->use_out_ep = !opts->no_out_endpoint;
 
+	++opts->refcnt;
 	mutex_unlock(&opts->lock);
 
 	hidg->func.name    = "hid";
@@ -1313,6 +1308,12 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 	hidg->qlen	   = 4;
 
 	return &hidg->func;
+
+err_put_device:
+	put_device(&hidg->dev);
+err_unlock:
+	mutex_unlock(&opts->lock);
+	return ERR_PTR(ret);
 }
 
 DECLARE_USB_FUNCTION_INIT(hid, hidg_alloc_inst, hidg_alloc);
-- 
2.38.1