Panic when trying to load malformed filesystem

fn main() {
    let data = b"\x00\xfe\xf7\xf7\xf7\xf7\xf7\xf7\xb7\xf7\x00\x00\x02\x10\x00\xfc\x01\x00\x00\x00\x00\x00\x00\x00\x002222\x01\x00\x00\x0022222\xfc\x00\x00\x00\x00\x00\x00\x00222[[[[[21[[[[[[[[[[[[[[[[[[[[[[[222[[2222\x91\x91\x91\x91\x00\x00\x00\x00\xaa\xaa\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xb2\xb2\xb2\xb2\xb2\xb2\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xbe&\x00\x00\x00\x00\x00\x00\x00\xbez\x00\x01\x00\xd0\x00-\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x012\x94\x94\x94\x94\x94\x9422222222222222222222222222\x01\x00\x00\x0022222\xe1222222222221[[[[[[[[[[[[K\x1b[[[[[[[[[[[[\x00\x00\x00\x00\x00\x00\x00\x00\x012\x94\x94\x94\x94\x94\x94\xf7\xf7\xf7\xf7\xf73\x00\xaa\xaa\x11\x03\x00\x00\x002222222222222222222222\x00\x00\x00\x00\xaa\xaa\xe7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\xf7\x00\x00\x00\x00\x00\x00\x00\x11\x00\x00\x00\x00\x00\x00\x00\xaa\xaa\xaa\x02\x00\x98\x00\x00\x00\x002222\x01\x00\x00\x0022222\xfc\x00\x00\x00\x00\x00\x00\x00222[[[[[21[[[[[[[[[[[[[[[[[[[[[[[222[[2222\x91\x91\x91\x91\x91\x91\xd4\x91\x91\x91\x91t\x912222222222222222\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\xaa\xaa\xaa\xaa\xaa\xaa\xaa\x00\x00\x01\x00\x00\x00\xaa\xaa\x9cU\xaa\xaa\x01\xaa2\xaa\xff\xff\xff\xff\xff\xff\xff\x02]\x00\x01\xff";

    let storage = std::io::Cursor::new(data.to_vec());
    fatfs::FileSystem::new(storage, fatfs::FsOptions::new());
}

This panics with a multiply overflow error.

[rafalh]

Is this a valid FAT filesystem or a manually crafted data with a goal to crash the lib?
I can see multiple places where overflow could happen and I believe it would be better to just return errors in such cases but I also believe those cases should not occur in real world normally.
One option to handle this would be changing all multiplications to checked_mul() and somehow pass the error to the FileSystem::new function but I don't like how it would make all multiplications ugly

Manually crafted, but I figured that bad behavior due to corrupted/malicious filesystems are in scope, you wouldn't want some OS to crash just because it's trying to read a filesystem with bad data.

Unfortunately, yeah, I'm not aware of any cleaner way than manually doing checked operations and propagating any errors upwards.