From 308399a179a49b7b858c725de10177fdb0502fd2 Mon Sep 17 00:00:00 2001
From: Andre Albsmeier <mail@fbsd2.e4m.org>
Date: Mon, 19 Aug 2024 10:54:24 +0300
Subject: [PATCH] tail -F: fix crash

When show() detects an error and closes the file and follow() wants to
close it again, a NULL dereference occurs.

PR:	280910
MFC after:	1 week
---
 usr.bin/tail/forward.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
index a5303385a74..6d9db94a827 100644
--- a/usr.bin/tail/forward.c
+++ b/usr.bin/tail/forward.c
@@ -379,7 +379,8 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 				    sb2.st_dev != file->st.st_dev ||
 				    sb2.st_nlink == 0) {
 					show(file);
-					fclose(file->fp);
+					if (file->fp != NULL)
+						fclose(file->fp);
 					file->fp = ftmp;
 					memcpy(&file->st, &sb2,
 					    sizeof(struct stat));