KEYS: Add invalidation support

Add support for invalidating a key - which renders it immediately invisible to
further searches and causes the garbage collector to immediately wake up,
remove it from keyrings and then destroy it when it's no longer referenced.

It's better not to do this with keyctl_revoke() as that marks the key to start
returning -EKEYREVOKED to searches when what is actually desired is to have the
key refetched.

To invalidate a key the caller must be granted SEARCH permission by the key.
This may be too strict.  It may be better to also permit invalidation if the
caller has any of READ, WRITE or SETATTR permission.

The primary use for this is to evict keys that are cached in special keyrings,
such as the DNS resolver or an ID mapper.

Signed-off-by: David Howells <dhowells@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/security/keys/compat.c b/security/keys/compat.c
index 4c48e13448f..fab4f8dda6c 100644
--- a/security/keys/compat.c
+++ b/security/keys/compat.c
@@ -135,6 +135,9 @@ asmlinkage long compat_sys_keyctl(u32 option,
                 return compat_keyctl_instantiate_key_iov(
                         arg2, compat_ptr(arg3), arg4, arg5);
 
+        case KEYCTL_INVALIDATE:
+                return keyctl_invalidate_key(arg2);
+
         default:
                 return -EOPNOTSUPP;
         }