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    Subject[PATCH 4.4 008/114] media: uvcvideo: fix division by zero at stream start
    Date
    From: Johan Hovold <johan@kernel.org>

    commit 8aa637bf6d70d2fb2ad4d708d8b9dd02b1c095df upstream.

    Add the missing bulk-endpoint max-packet sanity check to
    uvc_video_start_transfer() to avoid division by zero in
    uvc_alloc_urb_buffers() in case a malicious device has broken
    descriptors (or when doing descriptor fuzz testing).

    Note that USB core will reject URBs submitted for endpoints with zero
    wMaxPacketSize but that drivers doing packet-size calculations still
    need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
    endpoint descriptors with maxpacket=0")).

    Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
    Cc: stable@vger.kernel.org # 2.6.26
    Signed-off-by: Johan Hovold <johan@kernel.org>
    Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
    Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/media/usb/uvc/uvc_video.c | 4 ++++
    1 file changed, 4 insertions(+)

    --- a/drivers/media/usb/uvc/uvc_video.c
    +++ b/drivers/media/usb/uvc/uvc_video.c
    @@ -1720,6 +1720,10 @@ static int uvc_init_video(struct uvc_str
    if (ep == NULL)
    return -EIO;

    + /* Reject broken descriptors. */
    + if (usb_endpoint_maxp(&ep->desc) == 0)
    + return -EIO;
    +
    ret = uvc_init_video_bulk(stream, ep, gfp_flags);
    }


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