From 7f8ab2d2a5fd18dde322a3e37ee6f7161b686e35 Mon Sep 17 00:00:00 2001
From: Renaud Fivet <renaud.fivet@gmail.com>
Date: Tue, 2 May 2017 12:15:19 +0800
Subject: [PATCH] Avoid copy to buffer name using same source as destination to
 accomodate sensitive implementation of str(n)cpy.

---
 file.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/file.c b/file.c
index 50208de..d1bce00 100644
--- a/file.c
+++ b/file.c
@@ -283,8 +283,10 @@ int readin(const char *fname, boolean lockfl)
 		return status ;
 
 	bp->b_flag &= ~(BFINVS | BFCHG);
-	strncpy( bp->b_fname, fname, sizeof( fname_t) - 1) ;
-	bp->b_fname[ sizeof( fname_t) - 1] = '\0' ;
+	if( fname != bp->b_fname) { /* Copy if source differs from destination */
+		strncpy( bp->b_fname, fname, sizeof( fname_t) - 1) ;
+		bp->b_fname[ sizeof( fname_t) - 1] = '\0' ;
+	}
 
 	/* let a user macro get hold of things...if he wants */
 	execute(META | SPEC | 'R', FALSE, 1);