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media: usbvision: Fix invalid accesses after device disconnect

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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>
This commit is contained in:
Alan Stern 2019-10-07 12:09:04 -03:00 committed by Mauro Carvalho Chehab
parent 59251a8be3
commit c7a1914640
1 changed files with 6 additions and 2 deletions
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8
drivers/media/usb/usbvision/usbvision-video.c
View File

@ -453,6 +453,9 @@ static int vidioc_querycap(struct file *file, void *priv,
{
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,
@ -1099,8 +1102,9 @@ static int usbvision_radio_close(struct file *file)
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;