bin/159750: [PATCH] /usr/bin/tail can call fclose(NULL) causing core dump

[Steve Wills]

>Number:         159750
>Category:       bin
>Synopsis:       [PATCH] /usr/bin/tail can call fclose(NULL) causing core dump
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Aug 13 22:50:07 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Steve Wills
>Release:        
>Organization:
>Environment:
>Description:
I've been getting core dumps from tail when the FS it's on disappears. It can call fclose with a NULL argument, which causes the crash.
>How-To-Repeat:
run tail -F /path/to/file/on/md, then destroy the md(4)
>Fix:
See attached.

Patch attached with submission follows:

--- usr.bin/tail/forward.c.orig	2011-08-13 18:04:19.054770069 -0400
+++ usr.bin/tail/forward.c	2011-08-13 18:04:23.822771648 -0400
@@ -361,7 +361,9 @@
 					if (errno != ENOENT)
 						ierr(file->file_name);
 					show(file);
-					fclose(file->fp);
+					if (file->fp != NULL) {
+						fclose(file->fp);
+					}
 					file->fp = NULL;
 					ev_change++;
 					continue;


>Release-Note:
>Audit-Trail:
>Unformatted: