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Date:   Wed, 17 Aug 2022 22:55:14 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     linux-nfs@vger.kernel.org
Cc:     Olga Kornievskaia <kolga@netapp.com>, linux-fsdevel@vger.kernel.org
Subject: [RFC] problems with alloc_file_pseudo() use in __nfs42_ssc_open()
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Sender: Al Viro <viro@ftp.linux.org.uk>
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	My apologies for having missed that back when the SSC
patchset had been done (and missing the problems after it got
merged, actually).

1) if this
        r_ino = nfs_fhget(ss_mnt->mnt_sb, src_fh, fattr);
in __nfs42_ssc_open() yields a directory inode, we are screwed
as soon as it's passed to alloc_file_pseudo() - a *lot* of places
in dcache handling would break if we do that.  It's not too
nice for a regular file from non-cooperating filesystem, but for
directory ones it's deadly.

2) if alloc_file_pseudo() fails there, we get an inode leak.  It
needs an iput() for that case.  As in
        if (IS_ERR(filep)) {
		res = ERR_CAST(filep);
		iput(r_ino);
		goto out_free_name;
	}

But I'd like to point out that alloc_file_pseudo() is not inteded for
use on normal filesystem's inodes - the use here *mostly* works
(directories aside), but...  Use it on filesystem with non-trivial
default dentry_operations and things will get interesting, etc.