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@xxxxxxxxxxxx>
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))
