Re: [PATCH 1/5] fscrypt: clean up and improve dentry revalidation

[Al Viro <viro@xxxxxxxxxxxxxxxxxx>]

On Sun, Mar 17, 2019 at 01:04:40PM -0700, Eric Biggers wrote:
> +	/*
> +	 * Ciphertext name; valid if the directory's key is still unavailable.
> +	 *
> +	 * Note: since fscrypt forbids rename() on ciphertext names, it should
> +	 * be safe to access ->d_parent directly here.

No, it is not.  Again, d_splice_alias() on buggered fs image picking a reference
to your subdirectory when doing a lookup elsewhere.  It can relocate the
damn thing, without rename() being allowed for _anything_.

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