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From: Amir Goldstein <amir73il@gmail.com>
Date: Sat, 12 May 2018 07:49:21 +0300
Message-ID: <CAOQ4uxi7Dk=th3ZwBHpxY+yF45-0FKbEXqwRB8HeH_CBr0HAOQ@mail.gmail.com>
Subject: Re: [RFC][PATCH] ovl_create_index(): vfs_mkdir() might succeed
 leaving dentry negative unhashed
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Miklos Szeredi <miklos@szeredi.hu>
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On Sat, May 12, 2018 at 4:25 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> [same story as with the previous two patches]
>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
> diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
> index 8bede0742619..cdd8f8816d2a 100644
> --- a/fs/overlayfs/copy_up.c
> +++ b/fs/overlayfs/copy_up.c
> @@ -373,6 +373,22 @@ static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
>         if (err)
>                 goto out;
>
> +       if (unlikely(d_unhashed(temp))) {
> +               struct dentry *d = lookup_one_len(temp->d_name.name,
> +                                                 temp->d_parent,
> +                                                 temp->d_name.len);
> +               if (IS_ERR(d)) {
> +                       err = PTR_ERR(d);
> +                       goto out;
> +               }
> +               dput(temp);
> +               temp = d;
> +               if (d_is_negative(temp)) {
> +                       err = -EIO;
> +                       goto out;
> +               }
> +       }
> +

:-/ this pattern is too nasty to be open codes twice in ovl and
once in knfsd.
For ovl, we can hoist this into the ovl_do_mkdir() helper, but
what filesystems really need is vfs_mkdir_hashed(), then knfsd
can use it as well.

Thanks,
Amir.