• Jacob Keller's avatar
    ptp: correctly disable flags on old ioctls · 2df4de16
    Jacob Keller authored
    Commit 41560658
    
     ("PTP: introduce new versions of IOCTLs",
    2019-09-13) introduced new versions of the PTP ioctls which actually
    validate that the flags are acceptable values.
    
    As part of this, it cleared the flags value using a bitwise
    and+negation, in an attempt to prevent the old ioctl from accidentally
    enabling new features.
    
    This is incorrect for a couple of reasons. First, it results in
    accidentally preventing previously working flags on the request ioctl.
    By clearing the "valid" flags, we now no longer allow setting the
    enable, rising edge, or falling edge flags.
    
    Second, if we add new additional flags in the future, they must not be
    set by the old ioctl. (Since the flag wasn't checked before, we could
    potentially break userspace programs which sent garbage flag data.
    
    The correct way to resolve this is to check for and clear all but the
    originally valid flags.
    
    Create defines indicating which flags are correctly checked and
    interpreted by the original ioctls. Use these to clear any bits which
    will not be correctly interpreted by the original ioctls.
    
    In the future, new flags must be added to the VALID_FLAGS macros, but
    *not* to the V1_VALID_FLAGS macros. In this way, new features may be
    exposed over the v2 ioctls, but without breaking previous userspace
    which happened to not clear the flags value properly. The old ioctl will
    continue to behave the same way, while the new ioctl gains the benefit
    of using the flags fields.
    
    Cc: Richard Cochran <richardcochran@gmail.com>
    Cc: Felipe Balbi <felipe.balbi@linux.intel.com>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Christopher Hall <christopher.s.hall@intel.com>
    Signed-off-by: default avatarJacob Keller <jacob.e.keller@intel.com>
    Acked-by: default avatarRichard Cochran <richardcochran@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    2df4de16