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Date:   Wed, 13 Nov 2019 01:55:34 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Aleksa Sarai <cyphar@cyphar.com>
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Subject: Re: [PATCH v15 4/9] namei: LOOKUP_BENEATH: O_BENEATH-like scoped
 resolution
Message-ID: <20191113015534.GA26530@ZenIV.linux.org.uk>
References: <20191105090553.6350-1-cyphar@cyphar.com>
 <20191105090553.6350-5-cyphar@cyphar.com>
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On Tue, Nov 05, 2019 at 08:05:48PM +1100, Aleksa Sarai wrote:

Minor nit here - I'd split "move the conditional call of set_root()
into nd_jump_root()" into a separate patch before that one.  Makes
for fewer distractions in this one.  I'd probably fold "and be
ready for errors other than -ECHILD" into the same preliminary
patch.

> +			/* Not currently safe for scoped-lookups. */
> +			if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
> +				return ERR_PTR(-EXDEV);

Also a candidate for doing in nd_jump_link()...

> @@ -1373,8 +1403,11 @@ static int follow_dotdot_rcu(struct nameidata *nd)
>  	struct inode *inode = nd->inode;
>  
>  	while (1) {
> -		if (path_equal(&nd->path, &nd->root))
> +		if (path_equal(&nd->path, &nd->root)) {
> +			if (unlikely(nd->flags & LOOKUP_BENEATH))
> +				return -EXDEV;

Umm...  Are you sure it's not -ECHILD?