• Johan Hovold's avatar
    TTY: fix tty_wait_until_sent on 64-bit machines · 0b6acc6c
    Johan Hovold authored
    commit 79fbf4a5 upstream.
    
    Fix overflow bug in tty_wait_until_sent on 64-bit machines, where an
    infinite timeout (0) would be passed to the underlying tty-driver's
    wait_until_sent-operation as a negative timeout (-1), causing it to
    return immediately.
    
    This manifests itself for example as tcdrain() returning immediately,
    drivers not honouring the drain flags when setting terminal attributes,
    or even dropped data on close as a requested infinite closing-wait
    timeout would be ignored.
    
    The first symptom  was reported by Asier LLANO who noted that tcdrain()
    returned prematurely when using the ftdi_sio usb-serial driver.
    
    Fix this by passing 0 rather than MAX_SCHEDULE_TIMEOUT (LONG_MAX) to the
    underlying tty driver.
    
    Note that the serial-core wait_until_sent-implementation is not affected
    by this bug due to a lucky chance (comparison to an unsigned maximum
    timeout), and neither is the cyclades one that had an explicit check for
    negative timeouts, but all other tty drivers appear to be affected.
    
    Fixes: 1da177e4 ("Linux-2.6.12-rc2")
    Reported-by: default avatarZIV-Asier Llano Palacios <asier.llano@cgglobal.com>
    Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
    Reviewed-by: default avatarPeter Hurley <peter@hurleysoftware.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
    0b6acc6c
tty_ioctl.c 31 KB