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From: David Laight <David.Laight@ACULAB.COM>
To: 'Ido Schimmel' <idosch@idosch.org>, Christoph Hellwig <hch@lst.de>
Cc: "David S. Miller" <davem@davemloft.net>,
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Subject: RE: [PATCH 19/26] net/ipv6: switch ipv6_flowlabel_opt to sockptr_t
Date: Mon, 27 Jul 2020 13:24:45 +0000
Message-ID: <8c747034a5b641d18734de5f4d3a7507@AcuMS.aculab.com> (raw)
In-Reply-To: <20200727121505.GA1804864@shredder>

From: Ido Schimmel
> Sent: 27 July 2020 13:15
> On Thu, Jul 23, 2020 at 08:09:01AM +0200, Christoph Hellwig wrote:
> > Pass a sockptr_t to prepare for set_fs-less handling of the kernel
> > pointer from bpf-cgroup.
> >
> > Note that the get case is pretty weird in that it actually copies data
> > back to userspace from setsockopt.
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > ---
> >  include/net/ipv6.h       |  2 +-
> >  net/ipv6/ip6_flowlabel.c | 16 +++++++++-------
> >  net/ipv6/ipv6_sockglue.c |  2 +-
> >  3 files changed, 11 insertions(+), 9 deletions(-)
> >
> > diff --git a/include/net/ipv6.h b/include/net/ipv6.h
> > index 262fc88dbd7e2f..4c9d89b5d73268 100644
> > --- a/include/net/ipv6.h
> > +++ b/include/net/ipv6.h
> > @@ -406,7 +406,7 @@ struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions *opt_space,
> >  					 struct ip6_flowlabel *fl,
> >  					 struct ipv6_txoptions *fopt);
> >  void fl6_free_socklist(struct sock *sk);
> > -int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen);
> > +int ipv6_flowlabel_opt(struct sock *sk, sockptr_t optval, int optlen);
> >  int ipv6_flowlabel_opt_get(struct sock *sk, struct in6_flowlabel_req *freq,
> >  			   int flags);
> >  int ip6_flowlabel_init(void);
> > diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
> > index 27ee6de9beffc4..6b3c315f3d461a 100644
> > --- a/net/ipv6/ip6_flowlabel.c
> > +++ b/net/ipv6/ip6_flowlabel.c
> > @@ -371,7 +371,7 @@ static int fl6_renew(struct ip6_flowlabel *fl, unsigned long linger, unsigned lo
> >
> >  static struct ip6_flowlabel *
> >  fl_create(struct net *net, struct sock *sk, struct in6_flowlabel_req *freq,
> > -	  char __user *optval, int optlen, int *err_p)
> > +	  sockptr_t optval, int optlen, int *err_p)
> >  {
> >  	struct ip6_flowlabel *fl = NULL;
> >  	int olen;
> > @@ -401,7 +401,8 @@ fl_create(struct net *net, struct sock *sk, struct in6_flowlabel_req *freq,
> >  		memset(fl->opt, 0, sizeof(*fl->opt));
> >  		fl->opt->tot_len = sizeof(*fl->opt) + olen;
> >  		err = -EFAULT;
> > -		if (copy_from_user(fl->opt+1, optval+CMSG_ALIGN(sizeof(*freq)), olen))
> > +		sockptr_advance(optval, CMSG_ALIGN(sizeof(*freq)));
> > +		if (copy_from_sockptr(fl->opt + 1, optval, olen))
> >  			goto done;
> >
> >  		msg.msg_controllen = olen;
> > @@ -604,7 +605,7 @@ static int ipv6_flowlabel_renew(struct sock *sk, struct in6_flowlabel_req *freq)
> >  }
> >
> >  static int ipv6_flowlabel_get(struct sock *sk, struct in6_flowlabel_req *freq,
> > -		void __user *optval, int optlen)
> > +		sockptr_t optval, int optlen)
> >  {
> >  	struct ipv6_fl_socklist *sfl, *sfl1 = NULL;
> >  	struct ip6_flowlabel *fl, *fl1 = NULL;
> > @@ -702,8 +703,9 @@ static int ipv6_flowlabel_get(struct sock *sk, struct in6_flowlabel_req *freq,
> >  		goto recheck;
> >
> >  	if (!freq->flr_label) {
> > -		if (copy_to_user(&((struct in6_flowlabel_req __user *) optval)->flr_label,
> > -				 &fl->label, sizeof(fl->label))) {
> > +		sockptr_advance(optval,
> > +				offsetof(struct in6_flowlabel_req, flr_label));
> 
> Christoph,
> 
> I see a regression with IPv6 flowlabel that I bisected to this patch.
> When passing '-F 0' to 'ping' the flow label should be random, yet it's
> the same every time after this patch.
> 
> It seems that the pointer is never advanced after the call to
> sockptr_advance() because it is passed by value and not by reference.
> Even if you were to pass it by reference I think you would later need to
> call sockptr_decrease() or something similar. Otherwise it is very
> error-prone.

Depending on the other checks you may also be able to cross from
user addresses to kernel ones.
At the minimum sockptr_advance() has to fail if the boundary
would be crossed.

> Maybe adding an offset to copy_to_sockptr() and copy_from_sockptr() is
> better?

The 'is this a kernel or user copy' needs to use the base
address from the system call.
So you do need the offset passed in to copy_to/from_sockptr().

Clearly churn can be reduced by using a #define or static inline
for the common case.

The alternative is to pass a 'fat pointer' through than can
contain an offset as well as the user/kernel bases and
expected length.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)


  parent reply index

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23  6:08 get rid of the address_space override in setsockopt v2 Christoph Hellwig
2020-07-23  6:08 ` [PATCH 01/26] bpfilter: fix up a sparse annotation Christoph Hellwig
2020-07-23 11:14   ` Luc Van Oostenryck
2020-07-23  6:08 ` [PATCH 02/26] net/bpfilter: split __bpfilter_process_sockopt Christoph Hellwig
2020-07-23  6:08 ` [PATCH 03/26] bpfilter: reject kernel addresses Christoph Hellwig
2020-07-23 14:42   ` David Laight
2020-07-23 14:44     ` 'Christoph Hellwig'
2020-07-23 14:56       ` David Laight
2020-07-23  6:08 ` [PATCH 04/26] net: add a new sockptr_t type Christoph Hellwig
2020-07-23 15:40   ` Jan Engelhardt
2020-07-23 16:40   ` Eric Dumazet
2020-07-23 16:44     ` Christoph Hellwig
2020-07-23  6:08 ` [PATCH 05/26] net: switch copy_bpf_fprog_from_user to sockptr_t Christoph Hellwig
2020-07-23  6:08 ` [PATCH 06/26] net: switch sock_setbindtodevice " Christoph Hellwig
2020-07-23  6:08 ` [PATCH 07/26] net: switch sock_set_timeout " Christoph Hellwig
2020-07-23  6:08 ` [PATCH 08/26] " Christoph Hellwig
2020-07-23  8:39   ` [MPTCP] " Matthieu Baerts
2020-07-23  6:08 ` [PATCH 09/26] net/xfrm: switch xfrm_user_policy " Christoph Hellwig
2020-07-23  6:08 ` [PATCH 10/26] netfilter: remove the unused user argument to do_update_counters Christoph Hellwig
2020-07-23  6:08 ` [PATCH 11/26] netfilter: switch xt_copy_counters to sockptr_t Christoph Hellwig
2020-07-23  6:08 ` [PATCH 12/26] netfilter: switch nf_setsockopt " Christoph Hellwig
2020-07-27 15:03   ` Jason A. Donenfeld
2020-07-27 15:06     ` Christoph Hellwig
2020-07-27 16:16       ` Jason A. Donenfeld
2020-07-27 16:23         ` Christoph Hellwig
2020-07-28  8:07           ` David Laight
2020-07-28  8:17             ` Jason A. Donenfeld
2020-07-27 16:16     ` Christoph Hellwig
2020-07-27 16:21       ` Jason A. Donenfeld
2020-07-23  6:08 ` [PATCH 13/26] bpfilter: switch bpfilter_ip_set_sockopt " Christoph Hellwig
2020-07-23 11:16   ` David Laight
2020-07-23 11:44     ` 'Christoph Hellwig'
2020-07-23  6:08 ` [PATCH 14/26] net/ipv4: switch ip_mroute_setsockopt " Christoph Hellwig
2020-07-23  6:08 ` [PATCH 15/26] net/ipv4: merge ip_options_get and ip_options_get_from_user Christoph Hellwig
2020-07-23  6:08 ` [PATCH 16/26] net/ipv4: switch do_ip_setsockopt to sockptr_t Christoph Hellwig
2020-07-23  6:08 ` [PATCH 17/26] net/ipv6: switch ip6_mroute_setsockopt " Christoph Hellwig
2020-07-23  6:09 ` [PATCH 18/26] net/ipv6: split up ipv6_flowlabel_opt Christoph Hellwig
2020-07-23  6:09 ` [PATCH 19/26] net/ipv6: switch ipv6_flowlabel_opt to sockptr_t Christoph Hellwig
2020-07-27 12:15   ` Ido Schimmel
2020-07-27 13:00     ` Christoph Hellwig
2020-07-27 13:33       ` Ido Schimmel
2020-07-27 16:15         ` Christoph Hellwig
2020-07-27 18:22           ` Ido Schimmel
2020-07-27 13:24     ` David Laight [this message]
2020-07-23  6:09 ` [PATCH 20/26] net/ipv6: factor out a ipv6_set_opt_hdr helper Christoph Hellwig
2020-07-23  6:09 ` [PATCH 21/26] net/ipv6: switch do_ipv6_setsockopt to sockptr_t Christoph Hellwig
2020-07-23  6:09 ` [PATCH 22/26] net/udp: switch udp_lib_setsockopt " Christoph Hellwig
2020-07-23  6:09 ` [PATCH 23/26] net/tcp: switch ->md5_parse " Christoph Hellwig
2020-07-23  6:09 ` [PATCH 24/26] net/tcp: switch do_tcp_setsockopt " Christoph Hellwig
2020-07-23  6:09 ` [PATCH 25/26] net: pass a sockptr_t into ->setsockopt Christoph Hellwig
2020-07-23  8:39   ` [MPTCP] " Matthieu Baerts
2020-08-06 22:21   ` Eric Dumazet
2020-08-07  7:21     ` Christoph Hellwig
2020-08-07  9:18     ` David Laight
2020-08-07 18:29       ` Eric Dumazet
2020-08-08 13:54         ` David Laight
2020-07-23  6:09 ` [PATCH 26/26] net: optimize the sockptr_t for unified kernel/user address spaces Christoph Hellwig
2020-07-24 22:43 ` get rid of the address_space override in setsockopt v2 David Miller
2020-07-26  7:03   ` Christoph Hellwig
2020-07-26  7:08     ` Andreas Schwab
2020-07-26  7:46     ` David Miller
2020-07-27  9:51   ` David Laight
2020-07-27 13:48     ` Al Viro
2020-07-27 14:09       ` David Laight

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