How to avoid stdin input that does not fit in buffer be sent to the shell in Linux 64-bit Intel (x86-64) assembly

Question

Edit: Title changed, as @Gunner pointed out that this is not a buffer overflow.

In reading user input from stdin with NR_read

Answer 1

The read syscall already has that protection built in. One other thing though: You shouldn't be explicitly using syscall. What if your code is taken to an x86-64 machine (which uses sysenter)? You should be using Linux's VDSO (virtual dynamic shared object), which contains code to do syscalls on all architectures, regardless as to wheather they support syscall, sysenter, or only int.