From: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>
commit 690c8b804ad2eafbd35da5d3c95ad325ca7d5061 upstream.
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>
Acked-by: Kees Cook <keescook@xxxxxxxxxxxx>
Fixes: 83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Nicolas Pitre <nico@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230710002645.v565c7xq5iddruse@begin
Acked-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_io.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/tty/tty_io.c
+++ b/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))
