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    Subject[PATCH 4.5 022/200] usb: gadget: f_fs: Fix use-after-free
    Date
    4.5-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Lars-Peter Clausen <lars@metafoo.de>

    commit 38740a5b87d53ceb89eb2c970150f6e94e00373a upstream.

    When using asynchronous read or write operations on the USB endpoints the
    issuer of the IO request is notified by calling the ki_complete() callback
    of the submitted kiocb when the URB has been completed.

    Calling this ki_complete() callback will free kiocb. Make sure that the
    structure is no longer accessed beyond that point, otherwise undefined
    behaviour might occur.

    Fixes: 2e4c7553cd6f ("usb: gadget: f_fs: add aio support")
    Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
    Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/usb/gadget/function/f_fs.c | 5 ++---
    1 file changed, 2 insertions(+), 3 deletions(-)

    --- a/drivers/usb/gadget/function/f_fs.c
    +++ b/drivers/usb/gadget/function/f_fs.c
    @@ -646,6 +646,7 @@ static void ffs_user_copy_worker(struct
    work);
    int ret = io_data->req->status ? io_data->req->status :
    io_data->req->actual;
    + bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD;

    if (io_data->read && ret > 0) {
    use_mm(io_data->mm);
    @@ -657,13 +658,11 @@ static void ffs_user_copy_worker(struct

    io_data->kiocb->ki_complete(io_data->kiocb, ret, ret);

    - if (io_data->ffs->ffs_eventfd &&
    - !(io_data->kiocb->ki_flags & IOCB_EVENTFD))
    + if (io_data->ffs->ffs_eventfd && !kiocb_has_eventfd)
    eventfd_signal(io_data->ffs->ffs_eventfd, 1);

    usb_ep_free_request(io_data->ep, io_data->req);

    - io_data->kiocb->private = NULL;
    if (io_data->read)
    kfree(io_data->to_free);
    kfree(io_data->buf);

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