linux-kernel - Re: [PATCH] afs: proc cells and rootcell are writeable

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Date:	Tue, 28 Jan 2014 20:56:44 +0000
From:	David Howells <dhowells@...hat.com>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-afs@...ts.infradead.org, Pali Roh??r <pali.rohar@...il.com>
Subject: Re: [PATCH] afs: proc cells and rootcell are writeable

Al Viro <viro@...IV.linux.org.uk> wrote:

> > ... and then making proc_create() only permit regular files (and complain
> > if the S_IFMT field is not zero)?
> 
> We already do: in proc_create_data() we have
>         struct proc_dir_entry *pde;
>         if ((mode & S_IFMT) == 0)
>                 mode |= S_IFREG;
> 
>         if (!S_ISREG(mode)) {
>                 WARN_ON(1);     /* use proc_mkdir() */
>                 return NULL;
>         }
> 
> proc_mkdir{,_data,_mode} are there for purpose.  Nobody had been insane
> enough to put FIFOs or sockets in procfs and anything else would need
> additional data anyway.  proc_symlink() is there, proc_mknod() isn't and
> nobody has complained yet.  Let's keep it that way, plese...

Should we then change the proc_create_data() to do:

	struct proc_dir_entry *pde;

	if (mode & S_IFMT) {
		WARN_ON(1);     /* use proc_mkdir() */
		return NULL;
	}
	mode |= S_IFREG;

and stop passing S_IFREG into it?

David
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