On 04/23/2017 01:02 PM, Jann Horn wrote:
On Sun, Apr 23, 2017 at 9:24 AM, Matt Brown <matt@xxxxxxxxx> wrote:
This patch adds struct user_namespace *owner_user_ns to the tty_struct.
Then it is set to current_user_ns() in the alloc_tty_struct function.
This is done to facilitate capability checks against the original user
namespace that allocated the tty.
E.g. ns_capable(tty->owner_user_ns,CAP_SYS_ADMIN)
This combined with the use of user namespace's will allow hardening
protections to be built to mitigate container escapes that utilize TTY
ioctls such as TIOCSTI.
See: https://bugzilla.redhat.com/show_bug.cgi?id=1411256
Signed-off-by: Matt Brown <matt@xxxxxxxxx>
---
drivers/tty/tty_io.c | 1 +
include/linux/tty.h | 2 ++
2 files changed, 3 insertions(+)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index e6d1a65..e774385 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3191,6 +3191,7 @@ struct tty_struct *alloc_tty_struct(struct tty_driver *driver, int idx)
tty->index = idx;
tty_line_name(driver, idx, tty->name);
tty->dev = tty_get_device(tty);
+ tty->owner_user_ns = current_user_ns();
Why are you not taking a reference to the userns?
current_user_ns() returns the user namespace of the current task. What
do you mean "not taking a reference to the userns?"
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