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    Subject[PATCH 4.4 34/86] ptp: free ptp device pin descriptors properly
    Date
    From: Vladis Dronov <vdronov@redhat.com>

    commit 75718584cb3c64e6269109d4d54f888ac5a5fd15 upstream.

    There is a bug in ptp_clock_unregister(), where ptp_cleanup_pin_groups()
    first frees ptp->pin_{,dev_}attr, but then posix_clock_unregister() needs
    them to destroy a related sysfs device.

    These functions can not be just swapped, as posix_clock_unregister() frees
    ptp which is needed in the ptp_cleanup_pin_groups(). Fix this by calling
    ptp_cleanup_pin_groups() in ptp_clock_release(), right before ptp is freed.

    This makes this patch fix an UAF bug in a patch which fixes an UAF bug.

    Reported-by: Antti Laakso <antti.laakso@intel.com>
    Fixes: a33121e5487b ("ptp: fix the race between the release of ptp_clock and cdev")
    Link: https://lore.kernel.org/netdev/3d2bd09735dbdaf003585ca376b7c1e5b69a19bd.camel@intel.com/
    Signed-off-by: Vladis Dronov <vdronov@redhat.com>
    Acked-by: Richard Cochran <richardcochran@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/ptp/ptp_clock.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/drivers/ptp/ptp_clock.c
    +++ b/drivers/ptp/ptp_clock.c
    @@ -175,6 +175,7 @@ static void ptp_clock_release(struct dev
    {
    struct ptp_clock *ptp = container_of(dev, struct ptp_clock, dev);

    + ptp_cleanup_pin_groups(ptp);
    mutex_destroy(&ptp->tsevq_mux);
    mutex_destroy(&ptp->pincfg_mux);
    ida_simple_remove(&ptp_clocks_map, ptp->index);
    @@ -275,9 +276,8 @@ int ptp_clock_unregister(struct ptp_cloc
    if (ptp->pps_source)
    pps_unregister_source(ptp->pps_source);

    - ptp_cleanup_pin_groups(ptp);
    -
    posix_clock_unregister(&ptp->clock);
    +
    return 0;
    }
    EXPORT_SYMBOL(ptp_clock_unregister);

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