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Date: Thu, 22 Mar 2001 07:09:15 -0800 (PST)
From: andrew@nfr.net
To: freebsd-gnats-submit@FreeBSD.org
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Subject: kern/26000: unchecked return in vm/swap_pager.c
Sender: owner-freebsd-bugs@FreeBSD.ORG
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>Number:         26000
>Category:       kern
>Synopsis:       unchecked return in vm/swap_pager.c
>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:   Thu Mar 22 07:10:02 PST 2001
>Closed-Date:
>Last-Modified:
>Originator:     Andrew Lambeth
>Release:        4.1 and 4.2
>Organization:
NFR Security
>Environment:
FreeBSD better.andrew.creep.net 4.1-RELEASE FreeBSD 4.1-RELEASE #0: Thu Feb 22 10:10:45 EST 2001     andrew@better.andrew.creep.net:/usr/src/sys/compile/BETTER  i386


>Description:
There is an unchecked return from zinit() at line 307 in vm/swap_pager.c

this call will return NULL if kmem malloc limits have been increased beyond 
a certain point (~800MB) by modifying the algorithm or limits in kmeminit().  

It is unlikely that anyone would experience this in any normal situation,
still it seems like there should be a panic there.
>How-To-Repeat:
Increase kmem malloc limits to >800MB and boot the kernel.  It will run
fine until the first time it tries to page out, and then crash by
dereferencing the NULL pointer swap_zone.
>Fix:
Index: swap_pager.c
===================================================================
RCS file: /big/cvs/freebsd_sys_41/vm/swap_pager.c,v
retrieving revision 1.1.1.1
retrieving revision 1.1.1.1.2.1
diff -r1.1.1.1 -r1.1.1.1.2.1
314a315,318
>       if(swap_zone == NULL) {
>               panic("swap_zone == NULL");
>       }
> 

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

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