[issue2131] mmap() with size == 0 returns ptr to ld-elf.so.2

New submission from Venkatesh Srinivas <[e-mail]>:

mmap passed a size of 0 with PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON returns
a pointer to the base of the mapped ld-elf.so.2 rather than an EINVAL, which is
the expected return for len = 0.

---

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

main() {
	char *buf = mmap(NULL, 0, PROT_READ|PROT_WRITE,
			MAP_PRIVATE|MAP_ANON, -1, 0);
	printf("%p \n", buf);
	pause();
}

demonstrates; look at /proc/<pid>/map after the mmap().

----------
messages: 10108
nosy: vsrinivas
status: unread
title: mmap() with size == 0 returns ptr to ld-elf.so.2

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<http://bugs.dragonflybsd.org/issue2131>
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