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    Subject[ 48/50] ipc/sem.c: synchronize the proc interface
    Date
    3.11-stable review patch.  If anyone has any objections, please let me know.

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

    From: Manfred Spraul <manfred@colorfullife.com>

    commit d8c633766ad88527f25d9f81a5c2f083d78a2b39 upstream.

    The proc interface is not aware of sem_lock(), it instead calls
    ipc_lock_object() directly. This means that simple semop() operations
    can run in parallel with the proc interface. Right now, this is
    uncritical, because the implementation doesn't do anything that requires
    a proper synchronization.

    But it is dangerous and therefore should be fixed.

    Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
    Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Rik van Riel <riel@redhat.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    ipc/sem.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    --- a/ipc/sem.c
    +++ b/ipc/sem.c
    @@ -2103,6 +2103,14 @@ static int sysvipc_sem_proc_show(struct
    struct sem_array *sma = it;
    time_t sem_otime;

    + /*
    + * The proc interface isn't aware of sem_lock(), it calls
    + * ipc_lock_object() directly (in sysvipc_find_ipc).
    + * In order to stay compatible with sem_lock(), we must wait until
    + * all simple semop() calls have left their critical regions.
    + */
    + sem_wait_array(sma);
    +
    sem_otime = get_semotime(sma);

    return seq_printf(s,



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