module: signature checking hook

We do a very simple search for a particular string appended to the module
(which is cache-hot and about to be SHA'd anyway).  There's both a config
option and a boot parameter which control whether we accept or fail with
unsigned modules and modules that are signed with an unknown key.

If module signing is enabled, the kernel will be tainted if a module is
loaded that is unsigned or has a signature for which we don't have the
key.

(Useful feedback and tweaks by David Howells <dhowells@redhat.com>)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ad7e2e5088c1..9b2b8d3ae3e0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1582,6 +1582,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         log everything. Information is printed at KERN_DEBUG
                         so loglevel=8 may also need to be specified.
 
+        module.sig_enforce
+                        [KNL] When CONFIG_MODULE_SIG is set, this means that
+                        modules without (valid) signatures will fail to load.
+                        Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
+                        is always true, so this option does nothing.
+
         mousedev.tap_time=
                         [MOUSE] Maximum time between finger touching and
                         leaving touchpad surface for touch to be considered