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TIOCSTI: always enable for CAP_SYS_ADMIN

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83efeeeb3d ("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>
Acked-by: Kees Cook <keescook@chromium.org>
Fixes: 83efeeeb3d ("tty: Allow TIOCSTI to be disabled")
Cc: stable@vger.kernel.org
Reported-by: Nicolas Pitre <nico@fluxnic.net>
Link: https://lore.kernel.org/r/20230710002645.v565c7xq5iddruse@begin
Acked-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Samuel Thibault 2023-07-10 02:26:45 +02:00 • committed by Greg Kroah-Hartman
parent fdf0eaf114
commit 690c8b804a
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/tty_io.c
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@ -2285,7 +2285,7 @@ static int tiocsti(struct tty_struct *tty, char __user *p)
char ch, mbz = 0; char ch, mbz = 0;
struct tty_ldisc *ld; struct tty_ldisc *ld;
if (!tty_legacy_tiocsti) if (!tty_legacy_tiocsti && !capable(CAP_SYS_ADMIN))
return -EIO; return -EIO;
if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN)) if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))