cifs: create a define for the max number of iov we need for a SMB2 set_info

So we don't overflow the io vector arrays accidentally
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/smb2inode.c

@@ -56,7 +56,7 @@ smb2_compound_op(const unsigned int xid, struct cifs_tcon *tcon,
 	struct kvec rsp_iov[3];
 	struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
 	struct kvec qi_iov[1];
-	struct kvec si_iov[3];  /* 2 + potential padding. */
+	struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
 	struct kvec close_iov[1];
 	struct smb2_query_info_rsp *qi_rsp = NULL;
 	int flags = 0;

fs/cifs/smb2pdu.h

@@ -1174,6 +1174,15 @@ struct smb2_query_info_rsp {
 	__u8   Buffer[1];
 } __packed;
 
+/*
+ * Maximum number of iovs we need for a set-info request.
+ * The largest one is rename/hardlink
+ * [0] : struct smb2_set_info_req + smb2_file_[rename|link]_info
+ * [1] : path
+ * [2] : compound padding
+ */
+#define SMB2_SET_INFO_IOV_SIZE 3
+
 struct smb2_set_info_req {
 	struct smb2_sync_hdr sync_hdr;
 	__le16 StructureSize; /* Must be 33 */