• Waiman Long's avatar
    locking/rwsem: Protect all writes to owner by WRITE_ONCE() · fb6a44f3
    Waiman Long authored
    Without using WRITE_ONCE(), the compiler can potentially break a
    write into multiple smaller ones (store tearing). So a read from the
    same data by another task concurrently may return a partial result.
    This can result in a kernel crash if the data is a memory address
    that is being dereferenced.
    
    This patch changes all write to rwsem->owner to use WRITE_ONCE()
    to make sure that store tearing will not happen. READ_ONCE() may
    not be needed for rwsem->owner as long as the value is only used for
    comparison and not dereferencing.
    Signed-off-by: default avatarWaiman Long <Waiman.Long@hpe.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Dave Chinner <david@fromorbit.com>
    Cc: Davidlohr Bueso <dave@stgolabs.net>
    Cc: Douglas Hatch <doug.hatch@hpe.com>
    Cc: Jason Low <jason.low2@hp.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Hurley <peter@hurleysoftware.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Scott J Norton <scott.norton@hpe.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: http://lkml.kernel.org/r/1463534783-38814-3-git-send-email-Waiman.Long@hpe.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    fb6a44f3
rwsem.h 1.95 KB