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Date: Wed, 22 Mar 2000 00:40:13 +0100 (CET)
From: Edwin.Groothuis@cgmd76206.chello.nl (mavetju@chello.nl)
Reply-To: Edwin.Groothuis@cgmd76206.chello.nl (mavetju@chello.nl)
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Subject: kern/17539: kernel panic when asking help in visual userconfig
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>Number:         17539
>Category:       kern
>Synopsis:       kernel panic when asking help in visual userconfig
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Tue Mar 21 15:50:01 PST 2000
>Closed-Date:
>Last-Modified:
>Originator:     Edwin Groothuis
>Release:        FreeBSD 3.4-RELEASE i386
>Organization:
-
>Environment:

	visual config help

>Description:

	When in the visual user configuration and I ask for help
	and press space several times to get aa the bottom, at the
	last time space is entered the kernel will stop with a
	kernel-panic.

	This is a fix to kern/14394

>How-To-Repeat:

	Reset your computer.
	Enter "boot user_config"
	Enter "visual"
	Enter "?" for help
	Press space a couple of times
	Computer will hang with a kernel panic

>Fix:

	The problem is when you are at the end of the help (i.e.
	helptext[line]=NULL) and getchar() is being called. At that
	moment delta=0. If you press space for the next page, the
	delta nor topline are changed because helptext[line]==NULL.
	Back at the top of the for(;;)-loop, delta is stil 0 (was
	not changed), line is set to 0, the if (delta) failes (so
	line is still 0), getchar() is ran, space is pressed,
	helptext[line] is checked and found valid, topline is
	increased, delta is set and back the helptext is displayed
	again with an invalid value of topline for helptext.

	In /sys/i386/i386/userconfig.c:

    static void
    helpscreen(void)
    {
	int         topline = 0;                    /* where we are in the text */
	int         c, delta = 1;
	char        prompt[80];
+	int	    line = 0;
		    
	for (;;)                                    /* loop until user quits */
	{       
-	    int	    line = 0;
     
	    /* display help text */
	    if (delta)
	    {
		clear();                            /* remove everything else */
		for (line = topline;
		     (line < (topline + 24)) && (helptext[line]);

	Perhaps there is a more elegant solution with working with
	topline instead of line at the checking for space, but this
	one works.

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


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