Re: [PATCH v2 1/2] fs: Improve and simplify copy_mount_options

[Willy Tarreau <w@1wt.eu>]

On Thu, Jun 16, 2016 at 08:08:22AM +0100, Al Viro wrote:
> On Thu, Jun 16, 2016 at 08:57:38AM +0200, Willy Tarreau wrote:
> > +	type = get_fs_type(fstype);
> > +	if (!type)
> > +		return NULL;
> > +
> >  	copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
> >  	if (!copy)
> >  		return ERR_PTR(-ENOMEM);
> >  
> > +	/* avoid reading a whole page if the FS only needs a string. */
> > +	if (!(type->fs_flags & FS_BINARY_MOUNTDATA)) {
> > +		strlcpy(copy, data, PAGE_SIZE);
> > +		return copy;
> 
> a) it leaks a file_system_type reference

I was not sure about this one, thanks for confirming.

> b) data is a userland pointer, for crying out loud!

Yep I noticed it and fixed it after sending. I was focused on the
data coming from kernel due to the discussion.

I also think that since there are only two call places for
copy_mount_options(), we may move the test there and switch
to copy_mount_string() instead depending on the fs type.

Thanks,
Willy