c
// Hypothetical code within key_set_expiry
int key_set_expiry(struct key *key, /* ... other parameters */ uint64_t expiry) {
    // ... (other code) 

    if (expiry > MAX_SAFE_EXPIRY) { // Assuming MAX_SAFE_EXPIRY is defined appropriately
        return -ERANGE; // Or handle the error differently
    }

    // ... (rest of the function to set expiry safely)
}
