[PATCH 5.10.y 1/2] usb: gadget: f_hid: tidy error handling in hidg_alloc

[Sasha Levin <sashal@kernel.org>]

From: John Keeping <john@metanate.com>

[ Upstream commit 944fe915d00d3cb1bacb1e77cabfb6dc82e6f8b8 ]

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.

Tested-by: Lee Jones <lee@kernel.org>
Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Reviewed-by: Lee Jones <lee@kernel.org>
Signed-off-by: John Keeping <john@metanate.com>
Link: https://lore.kernel.org/r/20221122123523.3068034-4-john@metanate.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 4f88d65def6f ("usb: gadget: f_hid: fix device reference leak in hidg_alloc()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 e3738a1aa9f483..7c5916caf61b30 100644
--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -1265,7 +1265,6 @@ 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;
 
 	spin_lock_init(&hidg->write_spinlock);
 	spin_lock_init(&hidg->read_spinlock);
@@ -1278,11 +1277,8 @@ static struct usb_function *hidg_alloc(struct usb_function_instance *fi)
 	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;
@@ -1293,14 +1289,13 @@ 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";
@@ -1315,6 +1310,12 @@ 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);
-- 
2.53.0