Re: FAILED: patch "[PATCH] usb: udc: core: Use lock when write to soft_connect" failed to apply to 4.4-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

On Mon, Jan 25, 2021 at 03:19:51PM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here is the backport.

--
Regards
Sudip

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From a2a1a8f2013e91b11f3db55d65b6c1ce3d51bf98 Mon Sep 17 00:00:00 2001
From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Date: Thu, 14 Jan 2021 00:09:51 -0800
Subject: [PATCH] usb: udc: core: Use lock when write to soft_connect

commit c28095bc99073ddda65e4f31f6ae0d908d4d5cd8 upstream

Use lock to guard against concurrent access for soft-connect/disconnect
operations when writing to soft_connect sysfs.

Fixes: 2ccea03a8f7e ("usb: gadget: introduce UDC Class")
Cc: stable@vger.kernel.org
Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/338ea01fbd69b1985ef58f0f59af02c805ddf189.1610611437.git.Thinh.Nguyen@synopsys.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sudip: manual backporting to old file]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/usb/gadget/udc/udc-core.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
index a6a1678cb927..c6859fdd74bc 100644
--- a/drivers/usb/gadget/udc/udc-core.c
+++ b/drivers/usb/gadget/udc/udc-core.c
@@ -612,10 +612,13 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
 		struct device_attribute *attr, const char *buf, size_t n)
 {
 	struct usb_udc		*udc = container_of(dev, struct usb_udc, dev);
+	ssize_t			ret;
 
+	mutex_lock(&udc_lock);
 	if (!udc->driver) {
 		dev_err(dev, "soft-connect without a gadget driver\n");
-		return -EOPNOTSUPP;
+		ret = -EOPNOTSUPP;
+		goto out;
 	}
 
 	if (sysfs_streq(buf, "connect")) {
@@ -627,10 +630,14 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
 		usb_gadget_udc_stop(udc);
 	} else {
 		dev_err(dev, "unsupported command '%s'\n", buf);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto out;
 	}
 
-	return n;
+	ret = n;
+out:
+	mutex_unlock(&udc_lock);
+	return ret;
 }
 static DEVICE_ATTR(soft_connect, S_IWUSR, NULL, usb_udc_softconn_store);
 
-- 
2.29.2