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Message-Id: <20170423072457.27120-1-matt@nmatt.com> Date: Sun, 23 Apr 2017 03:24:56 -0400 From: Matt Brown <matt@...tt.com> To: serge@...lyn.com, jmorris@...ei.org, gregkh@...uxfoundation.org, jslaby@...e.com, corbet@....net, keescook@...omium.org Cc: akpm@...ux-foundation.org, jannh@...gle.com, kernel-hardening@...ts.openwall.com, linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, Matt Brown <matt@...tt.com> Subject: [PATCH v2 1/2] tiocsti-restrict : Add owner user namespace to tty_struct 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@...tt.com> --- 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(); 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
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