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Date:   Tue, 20 Sep 2022 21:57:47 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Miklos Szeredi <mszeredi@redhat.com>
Cc:     linux-fsdevel@vger.kernel.org, Amir Goldstein <amir73il@gmail.com>,
        David Howells <dhowells@redhat.com>,
        Yu-li Lin <yulilin@google.com>,
        Chirantan Ekbote <chirantan@chromium.org>
Subject: Re: [PATCH v3 7/9] vfs: move open right after ->tmpfile()
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References: <20220920193632.2215598-1-mszeredi@redhat.com>
 <20220920193632.2215598-8-mszeredi@redhat.com>
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On Tue, Sep 20, 2022 at 09:36:30PM +0200, Miklos Szeredi wrote:

>  	inode = child->d_inode;

Better
	inode = file_inode(file);

so that child would be completely ignored after dput().

> +	error = vfs_tmpfile(mnt_userns, &path, file, op->mode);
> +	if (error)
>  		goto out2;
> -	dput(path.dentry);
> -	path.dentry = child;
> -	audit_inode(nd->name, child, 0);
> +	audit_inode(nd->name, file->f_path.dentry, 0);
>  	/* Don't check for other permissions, the inode was just created */
> -	error = may_open(mnt_userns, &path, 0, op->open_flag);

Umm...  I'm not sure that losing it is the right thing - it might
be argued that ->permission(..., MAY_OPEN) is to be ignored for
tmpfile (and the only thing checking for MAY_OPEN is nfs, which is
*not* going to grow tmpfile any time soon - certainly not with these
calling conventions), but you are also dropping the call of
security_inode_permission(inode, MAY_OPEN) and that's a change
compared to what LSM crowd used to get...