linux-kernel - [PATCH] usb: Add data checks in usbtmc

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Date:   Mon, 22 Mar 2021 20:47:17 -0700
From:   Lv Yunlong <lyl2019@...l.ustc.edu.cn>
To:     gregkh@...uxfoundation.org, linux-usb@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Lv Yunlong <lyl2019@...l.ustc.edu.cn>
Subject: [PATCH] usb: Add data checks in usbtmc_disconnect

In usbtmc_disconnect, data is got from intf with the
initial reference. There is no refcount inc operation
before usbmc_free_int(data). In usbmc_free_int(data),
the data may be freed.

But later in usbtmc_disconnect, there is another put
function of data. I think it is better to add necessary
checks to avoid the data being put twice. It could cause
errors in race.

Signed-off-by: Lv Yunlong <lyl2019@...l.ustc.edu.cn>
---
 drivers/usb/class/usbtmc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 74d5a9c5238a..e0438cb46386 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -2494,7 +2494,9 @@ static void usbtmc_disconnect(struct usb_interface *intf)
 	}
 	mutex_unlock(&data->io_mutex);
 	usbtmc_free_int(data);
-	kref_put(&data->kref, usbtmc_delete);
+
+	if (data->iin_ep_present && data->iin_urb)
+		kref_put(&data->kref, usbtmc_delete);
 }
 
 static void usbtmc_draw_down(struct usbtmc_file_data *file_data)
-- 
2.25.1