[PATCH 3/4] restrict unprivileged TIOCSTI tty ioctl

[Matt Brown]

this patch depends on patch 1 and 2

enforces restrictions on unprivileged users injecting commands
into other processes in the same tty session using the TIOCSTI ioctl

Signed-off-by: Matt Brown <m...@nmatt.com>
---
 drivers/tty/tty_io.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e6d1a65..31894e8 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -2296,11 +2296,15 @@ static int tty_fasync(int fd, struct file *filp, int on)
  *     FIXME: may race normal receive processing
  */
 
+int tiocsti_restrict = IS_ENABLED(CONFIG_SECURITY_TIOCSTI_RESTRICT);
+
 static int tiocsti(struct tty_struct *tty, char __user *p)
 {
        char ch, mbz = 0;
        struct tty_ldisc *ld;
 
+       if (tiocsti_restrict && !capable(CAP_SYS_ADMIN))
+               return -EPERM;
        if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
                return -EPERM;
        if (get_user(ch, p))
-- 
2.10.2