linux-kernel - Re: Racy /proc creations interfaces

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Date:	Thu, 28 Dec 2006 11:21:47 +0300
From:	Alexey Dobriyan <adobriyan@...nvz.org>
To:	Al Viro <viro@....linux.org.uk>
Cc:	linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: Re: Racy /proc creations interfaces

On Wed, Dec 27, 2006 at 01:56:24PM +0000, Al Viro wrote:
> On Wed, Dec 27, 2006 at 04:42:23PM +0300, Alexey Dobriyan wrote:
> > 
> >    	struct proc_entry_raw foo_pe_raw = {
> > 		.owner = THIS_MODULE,
> > 		.name = "foo",
> > 		.mode = 0644,
> > 		.read_proc = foo_read_proc,
> > 		.data = foo_data,
> > 		.parent = foo_parent,
> > 	};
> > 
> > 	pde = create_proc_entry(&foo_pe_raw);
> > 	if (!pde)
> > 		return -ENOMEM;
> > 
> >    where "struct proc_entry_raw" is cut down version of "struct proc_dir_entry"
> 
> Ewwwwwwwwwwwwwww
> 
> Please, please no.  Especially not .parent.  If anything, let's add a
> helper saying "it's all set up now".  And turn create_proc_entry()
> into a macro that would pass THIS_MODULE to underlying function and
> call that helper, so that simple cases wouldn't have to bother at all.

People are setting ->data after create_proc_entry():

drivers/zorro/proc.c:
   110	static int __init zorro_proc_attach_device(u_int slot)
   111	{
   112		struct proc_dir_entry *entry;
   113		char name[4];
   114	
   115		sprintf(name, "%02x", slot);
   116		entry = create_proc_entry(name, 0, proc_bus_zorro_dir);
   117		if (!entry)
   118			return -ENOMEM;
   119		entry->proc_fops = &proc_bus_zorro_operations;
   120		entry->data = &zorro_autocon[slot];
   121		entry->size = sizeof(struct zorro_dev);

If create_proc_entry is a macro doing what you suggest (am I right?)

	#define create_proc_entry(name, mode, parent)
	({
		struct proc_dir_entry *pde;

		pde = __create_proc_entry(name, mode, parent, THIS_MODULE);
		if (pde)
			mark_proc_entry_ready(pde);
		pde;
	})

there is still a problem because we want it to be equivalent to

	pde = create_proc_entry(...);
	if (!pde)
		return -ENOMEM;
	pde->proc_fops = ...;
	pde->data = ...;
	mark_proc_entry_ready(pde);

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