Date: Sun, 10 Jul 2011 05:39:18 GMT From: Yui NARUSE <naruse@airemix.jp> To: freebsd-gnats-submit@FreeBSD.org Subject: kern/158755: mmap fails with addr=NULL, flags=MAP_STACK Message-ID: <201107100539.p6A5dIRQ034189@red.freebsd.org> Resent-Message-ID: <201107100540.p6A5e8Vk023551@freefall.freebsd.org>
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>Number: 158755
>Category: kern
>Synopsis: mmap fails with addr=NULL, flags=MAP_STACK
>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: Sun Jul 10 05:40:07 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator: Yui NARUSE
>Release: 8.2
>Organization:
>Environment:
FreeBSD windy.airemix.net 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Thu Feb 17 02:41:51 UTC 2011 root@mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64
>Description:
FreeBSD's mmap supports MAP_STACK as flags.
But when addr is NULL it won't find any suitable addr and try to use addr:0 and fails.
Note that manpage has following description and without MAP_STACK it find unallocated space and use it.
"If addr is zero, an address will be selected by the system. The actual starting address of the region is returned."
>How-To-Repeat:
Run following program. Both mmap should success but on FreeBSD 8.2 first one fails.
#include <sys/mman.h>
#include <stdio.h>
#include <errno.h>
int main (void) {
void *ptr;
errno = 0;
ptr = mmap((void *)0, 1, PROT_READ | PROT_WRITE, MAP_STACK, -1, 0);
printf("addr=0: ptr=%p, errno=%d\n", ptr, errno);
errno = 0;
ptr = mmap((void *)1, 1, PROT_READ | PROT_WRITE, MAP_STACK, -1, 0);
printf("addr=1: ptr=%p, errno=%d\n", ptr, errno);
return 0;
}
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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