Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

Pull security docs update from James Morris.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security: Minor improvements to no_new_privs documentation

2 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/prctl/no_new_privs.txt b/Documentation/prctl/no_new_privs.txt
index cb705ec69abe..f7be84fba910 100644
--- a/Documentation/prctl/no_new_privs.txt
+++ b/Documentation/prctl/no_new_privs.txt
@@ -25,6 +25,13 @@ bits will no longer change the uid or gid; file capabilities will not
 add to the permitted set, and LSMs will not relax constraints after
 execve.
 
+To set no_new_privs, use prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0).
+
+Be careful, though: LSMs might also not tighten constraints on exec
+in no_new_privs mode.  (This means that setting up a general-purpose
+service launcher to set no_new_privs before execing daemons may
+interfere with LSM-based sandboxing.)
+
 Note that no_new_privs does not prevent privilege changes that do not
 involve execve.  An appropriately privileged task can still call
 setuid(2) and receive SCM_RIGHTS datagrams.
diff --git a/include/linux/prctl.h b/include/linux/prctl.h
index 3988012255dc..289760f424aa 100644
--- a/include/linux/prctl.h
+++ b/include/linux/prctl.h
@@ -141,6 +141,8 @@
  * Changing LSM security domain is considered a new privilege.  So, for example,
  * asking selinux for a specific new context (e.g. with runcon) will result
  * in execve returning -EPERM.
+ *
+ * See Documentation/prctl/no_new_privs.txt for more details.
  */
 #define PR_SET_NO_NEW_PRIVS     38
 #define PR_GET_NO_NEW_PRIVS     39