Subject: Re: [PATCH 2/2] rtnetlink: Only supply IFLA_VF_PORTS information when RTEXT_FILTER_VF is set

From: David Gibson <[email-masked]>
Date: Thu, 24 Apr 2014 10:13:14 +1000

On Wed, Apr 23, 2014 at 11:17:15AM +0200, Jiri Pirko wrote:
> Wed, Apr 23, 2014 at 09:21:05AM CEST, [email-masked] wrote:
> >Since 115c9b81928360d769a76c632bae62d15206a94a (rtnetlink: Fix problem with
> >buffer allocation), RTM_NEWLINK messages only contain the IFLA_VFINFO_LIST
> >attribute if they were solicited by a GETLINK message containing an
> >IFLA_EXT_MASK attribute with the RTEXT_FILTER_VF flag.
> >
> >That was done because some user programs broke when they received more data
> >than expected - because IFLA_VFINFO_LIST contains information for each VF
> >it can become large if there are many VFs.
> >
> >However, the IFLA_VF_PORTS attribute, supplied for devices which implement
> >ndo_get_vf_port (currently the 'enic' driver only), has the same problem.
> >It supplies per-VF information and can therefore become large, but it is
> >not currently conditional on the IFLA_EXT_MASK value.
> >
> >Worse, it interacts badly with the existing EXT_MASK handling.  When
> >IFLA_EXT_MASK is not supplied, the buffer for netlink replies is fixed at
> >NLMSG_GOODSIZE.  If the information for IFLA_VF_PORTS exceeds this, then
> >rtnl_fill_ifinfo() returns -EMSGSIZE on the first message in a packet.
> >netlink_dump() will misinterpret this as having finished the listing and
> >omit data for this interface and all subsequent ones.  That can cause
> >getifaddrs(3) to enter an infinite loop.
> >
> >This patch addresses the problem by only supplying IFLA_VF_PORTS when
> >IFLA_EXT_MASK is supplied with the RTEXT_FILTER_VF flag set.
> >
> >Signed-off-by: David Gibson <[email-masked]>
> >---
> > net/core/rtnetlink.c | 16 ++++++++++------
> > 1 file changed, 10 insertions(+), 6 deletions(-)
> >
> >diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> >index 5331db2..32a1287 100644
> >--- a/net/core/rtnetlink.c
> >+++ b/net/core/rtnetlink.c
> >@@ -774,7 +774,8 @@ static inline int rtnl_vfinfo_size(const struct net_device *dev,
> > 		return 0;
> > }
> > 
> >-static size_t rtnl_port_size(const struct net_device *dev)
> >+static size_t rtnl_port_size(const struct net_device *dev,
> >+			     u32 ext_filter_mask)
> > {
> > 	size_t port_size = nla_total_size(4)		/* PORT_VF */
> > 		+ nla_total_size(PORT_PROFILE_MAX)	/* PORT_PROFILE */
> >@@ -790,7 +791,8 @@ static size_t rtnl_port_size(const struct net_device *dev)
> > 	size_t port_self_size = nla_total_size(sizeof(struct nlattr))
> > 		+ port_size;
> > 
> >-	if (!dev->netdev_ops->ndo_get_vf_port || !dev->dev.parent)
> >+	if (!dev->netdev_ops->ndo_get_vf_port || !dev->dev.parent
> >+	    || !(ext_filter_mask & RTEXT_FILTER_VF))
> 
> 	Do not start line with ||

Ah, sorry, I'm getting my project codingstyles mixed up.  Will fix.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson