linux-kernel - RE: ipv4: Use standard iovec primitive in raw_probe_proto

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Date:	Thu, 6 Nov 2014 09:55:31 +0000
From:	Jon Maloy <jon.maloy@...csson.com>
To:	Al Viro <viro@...IV.linux.org.uk>,
	Herbert Xu <herbert@...dor.apana.org.au>
CC:	David Miller <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bcrl@...ck.org" <bcrl@...ck.org>,
	"Masahide Nakamura" <nakam@...ux-ipv6.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: RE: ipv4: Use standard iovec primitive in raw_probe_proto_opt



> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Al Viro
> Sent: November-06-14 8:11 AM
> To: Herbert Xu
> Cc: David Miller; netdev@...r.kernel.org; linux-kernel@...r.kernel.org;
> bcrl@...ck.org; Masahide Nakamura; Hideaki YOSHIFUJI
> Subject: Re: ipv4: Use standard iovec primitive in raw_probe_proto_opt
> 
> On Thu, Nov 06, 2014 at 02:46:29PM +0800, Herbert Xu wrote:
> > On Thu, Nov 06, 2014 at 06:43:18AM +0000, Al Viro wrote:
> > > On Thu, Nov 06, 2014 at 01:50:23PM +0800, Herbert Xu wrote:
> > > > +	/* We only need the first two bytes. */
> > > > +	err = memcpy_fromiovecend((void *)&icmph, msg->msg_iov, 0, 2);
> > > > +	if (err)
> > > > +		return err;
> > > > +
> > > > +	fl4->fl4_icmp_type = icmph.type;
> > > > +	fl4->fl4_icmp_code = icmph.code;
> > >
> > > That's more readable, but that exposes another problem in there - we
> > > read the same piece of userland data twice, with no promise
> > > whatsoever that we'll get the same value both times...
> >
> > Sure, but you have to be root anyway to write to raw sockets.
> 
> Point, but that might very well be a pattern to watch for - there's at least one
> more instance in TIPC (also not exploitable, according to TIPC folks) and such

I don't recall this, and I can't see where it would be either. Can you please
point to where it is?

///jon

> bugs are easily repeated...
> 
> BTW, I've picked the tun and macvtap related bits from another part of old
> queue; see vfs.git#untested-macvtap - it's on top of #iov_iter-net and it's
> really completely untested.  Back then I was mostly interested in killing as
> many ->aio_write() instances as I could, so it's only the "send" side of things.
> --
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