From 497a82382bd211712ddbddcf381af875be8a37da Mon Sep 17 00:00:00 2001
From: Konstantin Belousov <kib@FreeBSD.org>
Date: Sun, 20 Sep 2009 12:40:56 +0000
Subject: [PATCH] Old (a.out) rtld attempts to mmap zero-length region, e.g.
 when bss of the linked object is zero-length. More old code assumes that mmap
 of zero length returns success.

For a.out and pre-8 ELF binaries, allow the mmap of zero length.

Reported by:	tegge
Reviewed by:	tegge, alc, jhb
MFC after:	3 days
---
 sys/vm/vm_mmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sys/vm/vm_mmap.c b/sys/vm/vm_mmap.c
index 2b99e3653df..c8d25ee3a30 100644
--- a/sys/vm/vm_mmap.c
+++ b/sys/vm/vm_mmap.c
@@ -64,6 +64,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/mount.h>
 #include <sys/conf.h>
 #include <sys/stat.h>
+#include <sys/sysent.h>
 #include <sys/vmmeter.h>
 #include <sys/sysctl.h>
 
@@ -229,7 +230,8 @@ mmap(td, uap)
 
 	fp = NULL;
 	/* make sure mapping fits into numeric range etc */
-	if (uap->len == 0 ||
+	if ((uap->len == 0 && !SV_CURPROC_FLAG(SV_AOUT) &&
+	     curproc->p_osrel >= 800104) ||
 	    ((flags & MAP_ANON) && uap->fd != -1))
 		return (EINVAL);