commit f0992098ca upstream.
Speakup exposing a line discipline allows userland to try to use it,
while it is deemed to be useless, and thus uselessly exposes potential
bugs. One of them is simply that in such a case if the line sends data,
spk_ttyio_receive_buf2 is called and crashes since spk_ttyio_synth
is NULL.
This change restricts the use of the speakup line discipline to
speakup drivers, thus avoiding such kind of issues altogether.
Cc: stable@vger.kernel.org
Reported-by: Shisong Qin <qinshisong1205@gmail.com>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Tested-by: Shisong Qin <qinshisong1205@gmail.com>
Link: https://lore.kernel.org/r/20201129193523.hm3f6n5xrn6fiyyc@function
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
b0d4fa10bf