selinux: delay inode label lookup as long as possible

Since looking up an inode's label can result in revalidation, delay
the lookup as long as possible to limit the performance impact.

Signed-off-by: Paul Moore <[e-mail]>

security/selinux/hooks.c

···
 					 u32 *_new_isid)
 {
 	const struct superblock_security_struct *sbsec = dir->i_sb->s_security;
-	const struct inode_security_struct *dsec = inode_security(dir);
 	const struct task_security_struct *tsec = current_security();
 
 	if ((sbsec->flags & SE_SBINITIALIZED) &&
···
 		   tsec->create_sid) {
 		*_new_isid = tsec->create_sid;
 	} else {
+		const struct inode_security_struct *dsec = inode_security(dir);
 		return security_transition_sid(tsec->sid, dsec->sid, tclass,
 					       name, _new_isid);
 	}
···
 	u32 sid = task_sid(to);
 	struct file_security_struct *fsec = file->f_security;
 	struct dentry *dentry = file->f_path.dentry;
-	struct inode_security_struct *isec = backing_inode_security(dentry);
+	struct inode_security_struct *isec;
 	struct common_audit_data ad;
 	int rc;
 
···
 	if (unlikely(IS_PRIVATE(d_backing_inode(dentry))))
 		return 0;
 
+	isec = backing_inode_security(dentry);
 	return avc_has_perm(sid, isec->sid, isec->sclass, file_to_av(file),
 			    &ad);
 }
···
 				  const void *value, size_t size, int flags)
 {
 	struct inode *inode = d_backing_inode(dentry);
-	struct inode_security_struct *isec = backing_inode_security(dentry);
+	struct inode_security_struct *isec;
 	struct superblock_security_struct *sbsec;
 	struct common_audit_data ad;
 	u32 newsid, sid = current_sid();
···
 	ad.type = LSM_AUDIT_DATA_DENTRY;
 	ad.u.dentry = dentry;
 
+	isec = backing_inode_security(dentry);
 	rc = avc_has_perm(sid, isec->sid, isec->sclass,
 			  FILE__RELABELFROM, &ad);
 	if (rc)
···
 					int flags)
 {
 	struct inode *inode = d_backing_inode(dentry);
-	struct inode_security_struct *isec = backing_inode_security(dentry);
+	struct inode_security_struct *isec;
 	u32 newsid;
 	int rc;
 
···
 		return;
 	}
 
+	isec = backing_inode_security(dentry);
 	isec->sclass = inode_mode_to_security_class(inode->i_mode);
 	isec->sid = newsid;
 	isec->initialized = LABEL_INITIALIZED;
···
 	u32 size;
 	int error;
 	char *context = NULL;
-	struct inode_security_struct *isec = inode_security(inode);
+	struct inode_security_struct *isec;
 
 	if (strcmp(name, XATTR_SELINUX_SUFFIX))
 		return -EOPNOTSUPP;
···
 	if (!error)
 		error = cred_has_capability(current_cred(), CAP_MAC_ADMIN,
 					    SECURITY_CAP_NOAUDIT);
+	isec = inode_security(inode);
 	if (!error)
 		error = security_sid_to_context_force(isec->sid, &context,
 						      &size);
···
 	struct common_audit_data ad;
 	struct file_security_struct *fsec = file->f_security;
 	struct inode *inode = file_inode(file);
-	struct inode_security_struct *isec = inode_security(inode);
+	struct inode_security_struct *isec;
 	struct lsm_ioctlop_audit ioctl;
 	u32 ssid = cred_sid(cred);
 	int rc;
···
 	if (unlikely(IS_PRIVATE(inode)))
 		return 0;
 
+	isec = inode_security(inode);
 	rc = avc_has_extended_perms(ssid, isec->sid, isec->sclass,
 			requested, driver, xperm, &ad);
 out:
···
 					SYSTEM__MODULE_LOAD, NULL);
 
 	/* finit_module */
+
 	ad.type = LSM_AUDIT_DATA_PATH;
 	ad.u.path = file->f_path;
 
-	isec = inode_security(file_inode(file));
 	fsec = file->f_security;
-
 	if (sid != fsec->sid) {
 		rc = avc_has_perm(sid, fsec->sid, SECCLASS_FD, FD__USE, &ad);
 		if (rc)
 			return rc;
 	}
 
+	isec = inode_security(file_inode(file));
 	return avc_has_perm(sid, isec->sid, SECCLASS_SYSTEM,
 				SYSTEM__MODULE_LOAD, &ad);
 }