seccomp: always propagate NO_NEW_PRIVS on tsync
Before this patch, a process with some permissive seccomp filter
that was applied by root without NO_NEW_PRIVS was able to add
more filters to itself without setting NO_NEW_PRIVS by setting
the new filter from a throwaway thread with NO_NEW_PRIVS.
Signed-off-by: Jann Horn <jann@thejh.net>
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 580ac2d..15a1795 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -316,24 +316,24 @@
put_seccomp_filter(thread);
smp_store_release(&thread->seccomp.filter,
caller->seccomp.filter);
+
+ /*
+ * Don't let an unprivileged task work around
+ * the no_new_privs restriction by creating
+ * a thread that sets it up, enters seccomp,
+ * then dies.
+ */
+ if (task_no_new_privs(caller))
+ task_set_no_new_privs(thread);
+
/*
* Opt the other thread into seccomp if needed.
* As threads are considered to be trust-realm
* equivalent (see ptrace_may_access), it is safe to
* allow one thread to transition the other.
*/
- if (thread->seccomp.mode == SECCOMP_MODE_DISABLED) {
- /*
- * Don't let an unprivileged task work around
- * the no_new_privs restriction by creating
- * a thread that sets it up, enters seccomp,
- * then dies.
- */
- if (task_no_new_privs(caller))
- task_set_no_new_privs(thread);
-
+ if (thread->seccomp.mode == SECCOMP_MODE_DISABLED)
seccomp_assign_mode(thread, SECCOMP_MODE_FILTER);
- }
}
}
