linux-kernel - Re: [PATCH 1/2] vfs: parse: deal with zero length string value

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Message-ID: <YrtAqQoyFG/6Y4un@ZenIV>
Date:   Tue, 28 Jun 2022 18:55:53 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Ian Kent <raven@...maw.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Siddhesh Poyarekar <siddhesh@...plt.org>,
        David Howells <dhowells@...hat.com>,
        Miklos Szeredi <miklos@...redi.hu>,
        Carlos Maiolino <cmaiolino@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] vfs: parse: deal with zero length string value

On Tue, Jun 28, 2022 at 08:30:52AM +0800, Ian Kent wrote:
> Parsing an fs string that has zero length should result in the parameter
> being set to NULL so that downstream processing handles it correctly.
> For example, the proc mount table processing should print "(none)" in
> this case to preserve mount record field count, but if the value points
> to the NULL string this doesn't happen.

	Hmmm...  And what happens if you feed that to ->parse_param(), which
calls fs_parse(), which decides that param->key looks like a name of e.g.
u32 option and calls fs_param_is_u32() to see what's what?  OOPS is a form
of rejection, I suppose, but...