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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Alan Stern <stern@rowland.harvard.edu>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        syzbot+7fa38a608b1075dfd634@syzkaller.appspotmail.com
Subject: [PATCH 5.3 72/95] media: usbvision: Fix invalid accesses after device disconnect
Date:   Wed, 27 Nov 2019 21:32:29 +0100
Message-Id: <20191127202938.704789013@linuxfoundation.org>
In-Reply-To: <20191127202845.651587549@linuxfoundation.org>
References: <20191127202845.651587549@linuxfoundation.org>
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From: Alan Stern <stern@rowland.harvard.edu>

commit c7a191464078262bf799136317c95824e26a222b upstream.

The syzbot fuzzer found two invalid-access bugs in the usbvision
driver.  These bugs occur when userspace keeps the device file open
after the device has been disconnected and usbvision_disconnect() has
set usbvision->dev to NULL:

	When the device file is closed, usbvision_radio_close() tries
	to issue a usb_set_interface() call, passing the NULL pointer
	as its first argument.

	If userspace performs a querycap ioctl call, vidioc_querycap()
	calls usb_make_path() with the same NULL pointer.

This patch fixes the problems by making the appropriate tests
beforehand.  Note that vidioc_querycap() is protected by
usbvision->v4l2_lock, acquired in a higher layer of the V4L2
subsystem.

Reported-and-tested-by: syzbot+7fa38a608b1075dfd634@syzkaller.appspotmail.com

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: <stable@vger.kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/media/usb/usbvision/usbvision-video.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- a/drivers/media/usb/usbvision/usbvision-video.c
+++ b/drivers/media/usb/usbvision/usbvision-video.c
@@ -453,6 +453,9 @@ static int vidioc_querycap(struct file *
 {
 	struct usb_usbvision *usbvision = video_drvdata(file);
 
+	if (!usbvision->dev)
+		return -ENODEV;
+
 	strscpy(vc->driver, "USBVision", sizeof(vc->driver));
 	strscpy(vc->card,
 		usbvision_device_data[usbvision->dev_model].model_string,
@@ -1111,8 +1114,9 @@ static int usbvision_radio_close(struct
 	mutex_lock(&usbvision->v4l2_lock);
 	/* Set packet size to 0 */
 	usbvision->iface_alt = 0;
-	usb_set_interface(usbvision->dev, usbvision->iface,
-				    usbvision->iface_alt);
+	if (usbvision->dev)
+		usb_set_interface(usbvision->dev, usbvision->iface,
+				  usbvision->iface_alt);
 
 	usbvision_audio_off(usbvision);
 	usbvision->radio = 0;