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    Subject[PATCH 4.4 130/342] posix-clock: Fix return code on the poll methods error path
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Richard Cochran <richardcochran@gmail.com>

    commit 1b9f23727abb92c5e58f139e7d180befcaa06fe0 upstream.

    The posix_clock_poll function is supposed to return a bit mask of
    POLLxxx values. However, in case the hardware has disappeared (due to
    hot plugging for example) this code returns -ENODEV in a futile
    attempt to throw an error at the file descriptor level. The kernel's
    file_operations interface does not accept such error codes from the
    poll method. Instead, this function aught to return POLLERR.

    The value -ENODEV does, in fact, contain the POLLERR bit (and almost
    all the other POLLxxx bits as well), but only by chance. This patch
    fixes code to return a proper bit mask.

    Credit goes to Markus Elfring for pointing out the suspicious
    signed/unsigned mismatch.

    Reported-by: Markus Elfring <elfring@users.sourceforge.net>
    igned-off-by: Richard Cochran <richardcochran@gmail.com>
    Cc: John Stultz <john.stultz@linaro.org>
    Cc: Julia Lawall <julia.lawall@lip6.fr>
    Link: http://lkml.kernel.org/r/1450819198-17420-1-git-send-email-richardcochran@gmail.com
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/time/posix-clock.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/kernel/time/posix-clock.c
    +++ b/kernel/time/posix-clock.c
    @@ -69,10 +69,10 @@ static ssize_t posix_clock_read(struct f
    static unsigned int posix_clock_poll(struct file *fp, poll_table *wait)
    {
    struct posix_clock *clk = get_posix_clock(fp);
    - int result = 0;
    + unsigned int result = 0;

    if (!clk)
    - return -ENODEV;
    + return POLLERR;

    if (clk->ops.poll)
    result = clk->ops.poll(clk, fp, wait);
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