* [PATCH] TIOCSTI: always enable for CAP_SYS_ADMIN
@ 2023-07-01 23:59 Samuel Thibault
2023-07-03 19:43 ` Kees Cook
0 siblings, 1 reply; 4+ messages in thread
From: Samuel Thibault @ 2023-07-01 23:59 UTC (permalink / raw)
To: Greg Kroah-Hartman, Randy Dunlap, Jiri Slaby, Simon Brand,
Kees Cook
Cc: stable, linux-kernel, Dave
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))
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] TIOCSTI: always enable for CAP_SYS_ADMIN
2023-07-01 23:59 [PATCH] TIOCSTI: always enable for CAP_SYS_ADMIN Samuel Thibault
@ 2023-07-03 19:43 ` Kees Cook
0 siblings, 0 replies; 4+ messages in thread
From: Kees Cook @ 2023-07-03 19:43 UTC (permalink / raw)
To: Samuel Thibault, Greg Kroah-Hartman, Randy Dunlap, Jiri Slaby,
Simon Brand, stable, linux-kernel, Dave
On Sun, Jul 02, 2023 at 01:59:18AM +0200, Samuel Thibault wrote:
> 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")
Based on the design of brltty, this appears to be the only solution. I
remain surprised that FreeBSD had no brltty support, which is why they
didn't run into this problem.
Acked-by: Kees Cook <keescook@chromium.org>
-Kees
>
> 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))
--
Kees Cook
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] TIOCSTI: always enable for CAP_SYS_ADMIN
@ 2023-07-10 0:26 Samuel Thibault
2023-07-13 6:01 ` Jiri Slaby
0 siblings, 1 reply; 4+ messages in thread
From: Samuel Thibault @ 2023-07-10 0:26 UTC (permalink / raw)
To: Greg Kroah-Hartman, Randy Dunlap, Jiri Slaby, Simon Brand,
Kees Cook
Cc: linux-kernel, Dave
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>
Acked-by: Kees Cook <keescook@chromium.org>
Fixes: 83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled")
Cc: stable@vger.kernel.org
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))
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] TIOCSTI: always enable for CAP_SYS_ADMIN
2023-07-10 0:26 Samuel Thibault
@ 2023-07-13 6:01 ` Jiri Slaby
0 siblings, 0 replies; 4+ messages in thread
From: Jiri Slaby @ 2023-07-13 6:01 UTC (permalink / raw)
To: Samuel Thibault, Greg Kroah-Hartman, Randy Dunlap, Simon Brand,
Kees Cook, linux-kernel, Dave
On 10. 07. 23, 2:26, Samuel Thibault wrote:
> 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>
> Acked-by: Kees Cook <keescook@chromium.org>
> Fixes: 83efeeeb3d04 ("tty: Allow TIOCSTI to be disabled")
> Cc: stable@vger.kernel.org
Acked-by: Jiri Slaby <jirislaby@kernel.org>
thanks,
--
js
suse labs
^ permalink raw reply [flat|nested] 4+ messages in thread
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