linux-kernel - Re: [PATCH 02/25] vfs: Allow fsinfo() to query what's in an fs

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Message-ID: <21652.1561122763@warthog.procyon.org.uk>
Date:   Fri, 21 Jun 2019 14:12:43 +0100
From:   David Howells <dhowells@...hat.com>
To:     Christian Brauner <christian@...uner.io>
Cc:     dhowells@...hat.com, viro@...iv.linux.org.uk, raven@...maw.net,
        linux-api@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, mszeredi@...hat.com
Subject: Re: [PATCH 02/25] vfs: Allow fsinfo() to query what's in an fs_context [ver #13]

Christian Brauner <christian@...uner.io> wrote:

> >  static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_kparams *params)
> >  {
> >  	struct fd f = fdget_raw(fd);
> 
> You're using fdget_raw() which means you want to allow O_PATH fds but
> below you're checking whether the f_ops correspond to
> fscontext_fops. If it's an O_PATH

It can't be.  The only way to get an fs_context fd is from fsopen() or
fspick() - neither of which allow O_PATH to be specified.

If you tried to go through /proc/pid/fd with open(O_PATH), I think you'd get
the symlink, not the target.

David