Overflows when adding/subtracting user-provided lengths

[albertvaka]

I wonder if there's a risk of out-of-bounds write when reading user-provided sizes and offsets and doing arithmetic operations with them. In network-facing libraries that deal with potential unsanitized input, I've often seen checks for overflow, eg:

int safe_subtract(int x, int y, int *result) {
    if (y > 0 && x < INT_MIN + y) {
        // Underflow would occur
        return 0;
    } else if (y < 0 && x > INT_MAX + y) {
        // Overflow would occur
        return 0;
    } else {
        // Safe to subtract
        *result = x - y;
        return 1;
    }
}