Excessive Memory Allocation on Large Image Dimensions in `image2::Image<T,C>::new`

[rfuzz]

While performing fuzz testing on the current library, I discovered an input that can cause a program crash. Specifically, when the width and height values of the image being read are extremely large, the function image2::image::Image<T,C>::new (image.rs:71) fails to initialize the vec, resulting in an abnormal program termination.

Here’s the relevant Rust code:

use image2::*;
fn main() {
    match Image::<f32, Rgb>::open("crash.bmp") {
        Ok(_) => { }
        Err(e) => {
            println!("Error: {:?}", e);
        }
    }
}

echo "Qk1CAAAAAAAAAD4AAAAoAAAAFc1bBxXNWwcBAAEAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAP///wCAAAAA" | base64 -d > crash.bmp

crash.bmp image info: biWidth 123456789, biHeight 123456789

When run, the following output is produced:

❯ valgrind ./target/debug/image2_fuzz_target_test
==1774007== Memcheck, a memory error detector
==1774007== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1774007== Using Valgrind-3.18.1 and LibVEX; rerun with -h for copyright info
==1774007== Command: ./target/debug/image2_fuzz_target_test
==1774007== 
memory allocation of 182898945002286252 bytes failed
==1774007== 
==1774007== Process terminating with default action of signal 6 (SIGABRT)
==1774007==    at 0x560C9FC: __pthread_kill_implementation (pthread_kill.c:44)
==1774007==    by 0x560C9FC: __pthread_kill_internal (pthread_kill.c:78)
==1774007==    by 0x560C9FC: pthread_kill@@GLIBC_2.34 (pthread_kill.c:89)
==1774007==    by 0x55B8475: raise (raise.c:26)
==1774007==    by 0x559E7F2: abort (abort.c:79)
==1774007==    by 0x1BA3E9: std::sys::pal::unix::abort_internal (mod.rs:373)
==1774007==    by 0x1B54D9: std::process::abort (process.rs:2366)
==1774007==    by 0x1BBB60: std::alloc::rust_oom (alloc.rs:376)
==1774007==    by 0x1BBB82: __rg_oom (alloc.rs:371)
==1774007==    by 0x1D1D8C: alloc::alloc::handle_alloc_error (alloc.rs:403)
==1774007==    by 0x1D1D79: alloc::raw_vec::handle_error (raw_vec.rs:776)
==1774007==    by 0x16A596: <T as alloc::vec::spec_from_elem::SpecFromElem>::from_elem (raw_vec.rs:438)
==1774007==    by 0x16A28B: alloc::vec::from_elem (mod.rs:3122)
==1774007==    by 0x14678D: image2::image::Image<T,C>::new (image.rs:71)
==1774007== 
==1774007== HEAP SUMMARY:
==1774007==     in use at exit: 30,157,440 bytes in 64,802 blocks
==1774007==   total heap usage: 117,217 allocs, 52,415 frees, 31,711,804 bytes allocated