linux-kernel - Re: [PATCH] virtio_console: fix sparse warnings

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Message-ID: <20150203234825.GA24626@kroah.com>
Date:	Tue, 3 Feb 2015 15:48:25 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Amit Shah <amit.shah@...hat.com>,
	Arnd Bergmann <arnd@...db.de>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_console: fix sparse warnings

On Mon, Dec 01, 2014 at 01:35:57PM +0200, Michael S. Tsirkin wrote:
> CHECK drivers/char/virtio_console.c
> drivers/char/virtio_console.c:687:36: warning: incorrect type in
> 	argument 1 (different address spaces)
> drivers/char/virtio_console.c:687:36:    expected void [noderef]
> 	<asn:1>*to
> drivers/char/virtio_console.c:687:36:    got char *out_buf
> drivers/char/virtio_console.c:790:35: warning: incorrect type in
> 	argument 2 (different address spaces)
> drivers/char/virtio_console.c:790:35:    expected char *out_buf
> drivers/char/virtio_console.c:790:35:    got char [noderef]
> 	<asn:1>*ubuf
> 
> fill_readbuf is reused with both kernel and userspace pointers,
> depending on value of to_user flag.

That's horrid, don't do that.  Have two different functions for this
type of thing, otherwise you defeat the whole purpose of trying to track
__user pointers.

thanks,

greg k-h
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