Quoting Matt Brown (matt@xxxxxxxxx): > 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 | 4 ++++ > include/linux/tty.h | 2 ++ > 2 files changed, 6 insertions(+) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index e6d1a65..03d5ea2 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -161,6 +161,7 @@ static void release_tty(struct tty_struct *tty, int idx); > * @tty: tty struct to free > * > * Free the write buffers, tty queue and tty memory itself. > + * Decrement the owner_user_ns count. > * > * Locking: none. Must be called after tty is definitely unused > */ > @@ -171,6 +172,7 @@ static void free_tty_struct(struct tty_struct *tty) > put_device(tty->dev); > kfree(tty->write_buf); > tty->magic = 0xDEADDEAD; > + atomic_dec(&tty->owner_user_ns->count); > kfree(tty); > } > > @@ -3191,6 +3193,8 @@ 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(); > + atomic_inc(&tty->owner_user_ns->count); Hi, CONFIG_USER_NS is an option, so unfortunately you need to do tty->owner_user_ns = get_user_ns(current_user_ns()); > > return tty; > } > diff --git a/include/linux/tty.h b/include/linux/tty.h > index 1017e904..d902d42 100644 > --- a/include/linux/tty.h > +++ b/include/linux/tty.h > @@ -12,6 +12,7 @@ > #include <uapi/linux/tty.h> > #include <linux/rwsem.h> > #include <linux/llist.h> > +#include <linux/user_namespace.h> > > > /* > @@ -333,6 +334,7 @@ struct tty_struct { > /* If the tty has a pending do_SAK, queue it here - akpm */ > struct work_struct SAK_work; > struct tty_port *port; > + struct user_namespace *owner_user_ns; > }; > > /* Each of a tty's open files has private_data pointing to tty_file_private */ > -- > 2.10.2 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
