Unsound usages of `VecFromRawParts`

[llooFlashooll]

Hi, I am scanning the ndarray in the latest version with my own static analyzer tool.

Unsafe conversion found at: src/data_repr.rs#L137

fn take_as_vec(&mut self) -> Vec<A>
{
   let capacity = self.capacity;
   let len = self.len;
   self.len = 0;
   self.capacity = 0;
   unsafe { Vec::from_raw_parts(self.ptr.as_ptr(), len, capacity) }
}

This unsound implementation of Vec::from_raw_parts would create a dangling pointer issues if the ptr is dropped automatically or is empty. The 'mem::forget' function can be used to avoid the issue.

This would potentially cause undefined behaviors in Rust. If we further manipulate the problematic converted types, it would potentially lead to different consequences such as uaf or double free. I am reporting this issue for your attention.

[bluss]

Thanks for the note - do you think that's an issue here, could you demonstrate the problem? ManuallyDrop is used several places in the same file (preferable to mem::forget in most cases).

[llooFlashooll]

Since my static analyzer may not be aware of this kind of semantic code, let me manually and carefully review and reply to you.

[bluss]

OwnedRepr is created from a Vec (OwnedRepr::from), which should be the basis for why this conversion is sound.

[llooFlashooll]

Thanks! I understand. Then there's no issue here. Sorry for any inconvenience I have caused.

[bluss]

No worries, thank you for taking a look, it helps!