83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled") broke BRLTTY's ability to simulate keypresses on the console, thus effectively breaking braille keyboards of blind users.
This restores the TIOCSTI feature for CAP_SYS_ADMIN processes, which BRLTTY is, thus fixing braille keyboards without re-opening the security issue.
Signed-off-by: Samuel Thibault samuel.thibault@ens-lyon.org Fixes: 83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled")
Index: linux-6.4/drivers/tty/tty_io.c =================================================================== --- linux-6.4.orig/drivers/tty/tty_io.c +++ linux-6.4/drivers/tty/tty_io.c @@ -2276,7 +2276,7 @@ static int tiocsti(struct tty_struct *tt char ch, mbz = 0; struct tty_ldisc *ld;
- if (!tty_legacy_tiocsti) + if (!tty_legacy_tiocsti && !capable(CAP_SYS_ADMIN)) return -EIO;
if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))