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Message-Id: <200205130516.g4D5GZh8027512@www.freebsd.org>
Date: Sun, 12 May 2002 22:16:35 -0700 (PDT)
From: David Xu <davidx@viasoft.com.cn>
To: freebsd-gnats-submit@FreeBSD.org
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Subject: i386/38016: i386_get_ldt range checking bug
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>Number:         38016
>Category:       i386
>Synopsis:       i386_get_ldt range checking bug
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun May 12 22:20:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     David Xu
>Release:        FreeBSD 5.0-CURRENT
>Organization:
Viatech
>Environment:
FreeBSD davidbsd.viasoft.com.cn 5.0-CURRENT FreeBSD 5.0-CURRENT #23: 
Mon May 13 12:16:30 CST 2002     
davidx@davidbsd.viasoft.com.cn:/usr/src/sys/i386/compile/xu  i386      

>Description:
function i386_get_ldt() in sys_machdep.c has range checking bug, it
allow program to access LDT out of bound, may cause page fault.

>How-To-Repeat:

>Fix:
--- /usr/src/sys/i386/i386/sys_machdep.c	Wed Apr  3 02:37:41 2002
+++ /usr/src/sys/i386/i386/sys_machdep.c.new	Mon May 13 11:11:19 2002
@@ -363,6 +363,7 @@
 	char *args;
 {
 	int error = 0;
+	int largest_ld;
 	struct proc_ldt *pldt = td->td_proc->p_md.md_ldt;
 	int nldt, num;
 	union descriptor *lp;
@@ -389,7 +390,8 @@
 		num = min(uap->num, nldt);
 		lp = &ldt[uap->start];
 	}
-	if (uap->start > nldt)
+	largest_ld = uap->start + num - 1;
+	if (uap->start >= nldt || largest_ld >= nldt)
 		return(EINVAL);
 
 	error = copyout(lp, uap->descs, num * sizeof(union descriptor));

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

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