linux-kernel - [PATCH] usb: idmouse: fix an uninit-value in idmouse

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Message-Id: <20220922134847.1101921-1-dzm91@hust.edu.cn>
Date:   Thu, 22 Sep 2022 21:48:44 +0800
From:   Dongliang Mu <dzm91@...t.edu.cn>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Dongliang Mu <mudongliangabcd@...il.com>,
        syzbot+79832d33eb89fb3cd092@...kaller.appspotmail.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] usb: idmouse: fix an uninit-value in idmouse_open

From: Dongliang Mu <mudongliangabcd@...il.com>

In idmouse_create_image, if any ftip_command fails, it will
go to the reset label. However, this leads to the data in
bulk_in_buffer[HEADER..IMGSIZE] uninitialized. And the check
for valid image incurs an uninitialized dereference.

Fix this by moving the check before reset label since this
check only be valid if the data after bulk_in_buffer[HEADER]
has concrete data.

Note that this is found by KMSAN, so only kernel compilation
is tested.

Reported-by: syzbot+79832d33eb89fb3cd092@...kaller.appspotmail.com
Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
---
 drivers/usb/misc/idmouse.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/misc/idmouse.c b/drivers/usb/misc/idmouse.c
index e9437a176518..ea39243efee3 100644
--- a/drivers/usb/misc/idmouse.c
+++ b/drivers/usb/misc/idmouse.c
@@ -177,10 +177,6 @@ static int idmouse_create_image(struct usb_idmouse *dev)
 		bytes_read += bulk_read;
 	}
 
-	/* reset the device */
-reset:
-	ftip_command(dev, FTIP_RELEASE, 0, 0);
-
 	/* check for valid image */
 	/* right border should be black (0x00) */
 	for (bytes_read = sizeof(HEADER)-1 + WIDTH-1; bytes_read < IMGSIZE; bytes_read += WIDTH)
@@ -192,6 +188,10 @@ static int idmouse_create_image(struct usb_idmouse *dev)
 		if (dev->bulk_in_buffer[bytes_read] != 0xFF)
 			return -EAGAIN;
 
+	/* reset the device */
+reset:
+	ftip_command(dev, FTIP_RELEASE, 0, 0);
+
 	/* should be IMGSIZE == 65040 */
 	dev_dbg(&dev->interface->dev, "read %d bytes fingerprint data\n",
 		bytes_read);
-- 
2.25.1