tty: Prevent untrappable signals from malicious program
tty: Prevent untrappable signals from malicious program

Commit 26df6d13406d1a5 ("tty: Add EXTPROC support for LINEMODE")
allows a process which has opened a pty master to send _any_ signal
to the process group of the pty slave. Although potentially
exploitable by a malicious program running a setuid program on
a pty slave, it's unknown if this exploit currently exists.

Limit to signals actually used.

Cc: Theodore Ts'o <4ed386e0495d3e109932df055831d9ec2f824927@mit.edu>
Cc: Howard Chu <bee6ab4c922836f6a558b1e8dbc393b81627d805@symas.com>
Cc: One Thousand Gnomes <71add150d99de1bd5a1ceb2e3464b76ba775ecb5@lxorguk.ukuu.org.uk>
Cc: Jiri Slaby <dfbf39eb5bf303a3db5454d815cb8c8888cbadf9@suse.cz>
Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org> # 2.6.36+
Signed-off-by: Peter Hurley <4b8373d016f277527198385ba72fda0feb5da015@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <4645f7897fd33786a2ee1264d590b3c400559d85@linuxfoundation.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs