Patched code sample

from PIL import Image

def fixed_bdf_char_parsing(bbx_string_from_font_file):
    """
    Simplified demonstration of the fix for the vulnerability. The original
    vulnerability existed because the dimensions were passed to Image.new()
    without the _decompression_bomb_check call.
    """
    # Attacker-controlled dimensions are parsed from the font file.
    # e.g., bbx_string_from_font_file = "50000 50000 0 0"
    w, h, x_offset, y_offset = [int(p) for p in bbx_string_from_font_file.split()]

    if w <= 0 or h <= 0:
        return None

    # THE FIX: Add a decompression bomb check before memory allocation.
    # This call was missing in the vulnerable versions.
    Image._decompression_bomb_check((w, h))

    # The vulnerable call is now protected. This line will only be reached
    # if the dimensions are considered safe by Pillow.
    im = Image.new("1", (w, h))

    return im