How to prevent leaving the current buffer when traversing the jump list in Vim?

Try the following jump-list traversing function. It steps successively from one jump-list location to another (using Ctrl+O or Ctrl+I depending on the values that are supplied to its back and forw arguments), and stops if the current location is in the same buffer as that buffer it has started from. If it is not possible to find a jump-list location that belongs to the current buffer, the function returns to the position in the jump list that was the current one before the function was called.

function! JumpWithinFile(back, forw)
    let [n, i] = [bufnr('%'), 1]
    let p = [n] + getpos('.')[1:]
    sil! exe 'norm!1' . a:forw
    while 1
        let p1 = [bufnr('%')] + getpos('.')[1:]
        if n == p1[0] | break | endif
        if p == p1
            sil! exe 'norm!' . (i-1) . a:back
            break
        endif
        let [p, i] = [p1, i+1]
        sil! exe 'norm!1' . a:forw
    endwhile
endfunction

To use this function as a Ctrl+O/Ctrl+I-replacement locked to the current buffer, create mappings as it is shown below.

nnoremap <silent> <c-k> :call JumpWithinFile("\<c-i>", "\<c-o>")<cr>
nnoremap <silent> <c-j> :call JumpWithinFile("\<c-o>", "\<c-i>")<cr>

Maybe the EnhancedJumps plugin will help.

With this plugin installed, the jump to another buffer is only done if the same jump command is repeated once more immediately afterwards.