mmap_repro.c

#include <unistd.h>
#include <sys/mman.h>
#include <err.h>
#include <stdio.h>
#include <fcntl.h>

int main()
{
	int ret = 0;
	char old_limit[64];
	int limlen = 0;
	int fd = open("/proc/sys/vm/mmap_min_addr", O_RDWR);
	if (fd < 0)
		err(1, "open");
	if ((limlen = read(fd, old_limit, sizeof(old_limit))) < 0)
		err(1, "read");
	lseek(fd, 0, SEEK_SET);
	if (write(fd, "0\n", 2) < 0)
		err(1, "write");

	void *addr = mmap(NULL, 0x1000, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0);
	if (addr == MAP_FAILED)
		err(1, "addr");
	/* test regression */
	if (mprotect(NULL, 0x1000, PROT_READ) < 0)
	{
		ret = 1;
		printf("Regression present!\n");
	}

	lseek(fd, 0, SEEK_SET);

	if (write(fd, old_limit, limlen) < 0)
		err(1, "write(old_limit)");
	return ret;
}