Description: speakup: Do not let the line discipline be used several times
References:
 https://www.openwall.com/lists/oss-security/2020/11/19/3
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git/commit/?h=tty-linus&id=d4122754442799187d5d537a9c039a49a67e57f1
Notes:
 carnil> Fixed as well in v5.9.11.
 bwh> Introduced in 4.13 by commit 1ab92da32e37 "staging: speakup: add
 bwh> tty-based comms functions".
Bugs:
upstream: released (5.10-rc5) [d4122754442799187d5d537a9c039a49a67e57f1]
4.19-upstream-stable: released (4.19.160) [3560603ef82f11277143a433170bca05bd9288a8]
4.9-upstream-stable: N/A "Vulnerable code not present"
sid: released (5.9.11-1)
4.19-buster-security: released (4.19.160-1)
4.9-stretch-security: N/A "Vulnerable code not present"