security: Add hook to invalidate inode security labels

Add a hook to invalidate an inode's security label when the cached
information becomes invalid.

Add the new hook in selinux: set a flag when a security label becomes
invalid.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <pmoore@redhat.com>
diff --git a/include/linux/security.h b/include/linux/security.h
index e79149a..4824a4c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -353,6 +353,7 @@
 int security_secctx_to_secid(const char *secdata, u32 seclen, u32 *secid);
 void security_release_secctx(char *secdata, u32 seclen);
 
+void security_inode_invalidate_secctx(struct inode *inode);
 int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
 int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
 int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
@@ -1093,6 +1094,10 @@
 {
 }
 
+static inline void security_inode_invalidate_secctx(struct inode *inode)
+{
+}
+
 static inline int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen)
 {
 	return -EOPNOTSUPP;