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    Subject[PATCH 5.14 19/24] comedi: vmk80xx: fix bulk-buffer overflow
    Date
    From: Johan Hovold <johan@kernel.org>

    commit 78cdfd62bd54af615fba9e3ca1ba35de39d3871d upstream.

    The driver is using endpoint-sized buffers but must not assume that the
    tx and rx buffers are of equal size or a malicious device could overflow
    the slab-allocated receive buffer when doing bulk transfers.

    Fixes: 985cafccbf9b ("Staging: Comedi: vmk80xx: Add k8061 support")
    Cc: stable@vger.kernel.org # 2.6.31
    Signed-off-by: Johan Hovold <johan@kernel.org>
    Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
    Link: https://lore.kernel.org/r/20211025114532.4599-5-johan@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/comedi/drivers/vmk80xx.c | 16 +++++++---------
    1 file changed, 7 insertions(+), 9 deletions(-)

    --- a/drivers/comedi/drivers/vmk80xx.c
    +++ b/drivers/comedi/drivers/vmk80xx.c
    @@ -159,22 +159,20 @@ static void vmk80xx_do_bulk_msg(struct c
    __u8 rx_addr;
    unsigned int tx_pipe;
    unsigned int rx_pipe;
    - size_t size;
    + size_t tx_size;
    + size_t rx_size;

    tx_addr = devpriv->ep_tx->bEndpointAddress;
    rx_addr = devpriv->ep_rx->bEndpointAddress;
    tx_pipe = usb_sndbulkpipe(usb, tx_addr);
    rx_pipe = usb_rcvbulkpipe(usb, rx_addr);
    -
    - /*
    - * The max packet size attributes of the K8061
    - * input/output endpoints are identical
    - */
    - size = usb_endpoint_maxp(devpriv->ep_tx);
    + tx_size = usb_endpoint_maxp(devpriv->ep_tx);
    + rx_size = usb_endpoint_maxp(devpriv->ep_rx);

    usb_bulk_msg(usb, tx_pipe, devpriv->usb_tx_buf,
    - size, NULL, devpriv->ep_tx->bInterval);
    - usb_bulk_msg(usb, rx_pipe, devpriv->usb_rx_buf, size, NULL, HZ * 10);
    + tx_size, NULL, devpriv->ep_tx->bInterval);
    +
    + usb_bulk_msg(usb, rx_pipe, devpriv->usb_rx_buf, rx_size, NULL, HZ * 10);
    }

    static int vmk80xx_read_packet(struct comedi_device *dev)

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