On Wed, Apr 10, 2019 at 09:16:26PM +0800, Yanjun Zhu wrote:
>
> On 2019/4/10 16:15, Leon Romanovsky wrote:
> > From: Parav Pandit <parav@xxxxxxxxxxxx>
> >
> > Use rdma_read_gid_attr_ndev_rcu() to access netdevice attached to GID
> > entry under rcu lock.
> >
> > This ensures that while working on the netdevice of the GID, it doesn't
> > get freed.
> >
> > Signed-off-by: Parav Pandit <parav@xxxxxxxxxxxx>
> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> > ---
> > drivers/infiniband/sw/rxe/rxe_net.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/infiniband/sw/rxe/rxe_net.c b/drivers/infiniband/sw/rxe/rxe_net.c
> > index c44139788afc..5a3474f9351b 100644
> > --- a/drivers/infiniband/sw/rxe/rxe_net.c
> > +++ b/drivers/infiniband/sw/rxe/rxe_net.c
> > @@ -458,7 +458,7 @@ struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
> > int paylen, struct rxe_pkt_info *pkt)
> > {
> > unsigned int hdr_len;
> > - struct sk_buff *skb;
> > + struct sk_buff *skb = NULL;
>
> In the following source code, skb is assigned before it is used. So is it
> necessary to initialize it now?
Yes, we need to initialize it, because we have an error unwind path
prior to skb reassignment, see rdma_read_gid_attr_ndev_rcu() in this
patch.
>
> Zhu Yanjun
>
> > struct net_device *ndev;
> > const struct ib_gid_attr *attr;
> > const int port_num = 1;
> > @@ -466,7 +466,6 @@ struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
> > attr = rdma_get_gid_attr(&rxe->ib_dev, port_num, av->grh.sgid_index);
> > if (IS_ERR(attr))
> > return NULL;
> > - ndev = attr->ndev;
> > if (av->network_type == RDMA_NETWORK_IPV4)
> > hdr_len = ETH_HLEN + sizeof(struct udphdr) +
> > @@ -475,16 +474,26 @@ struct sk_buff *rxe_init_packet(struct rxe_dev *rxe, struct rxe_av *av,
> > hdr_len = ETH_HLEN + sizeof(struct udphdr) +
> > sizeof(struct ipv6hdr);
> > + rcu_read_lock();
> > + ndev = rdma_read_gid_attr_ndev_rcu(attr);
> > + if (IS_ERR(ndev)) {
> > + rcu_read_unlock();
> > + goto out;
> > + }
> > skb = alloc_skb(paylen + hdr_len + LL_RESERVED_SPACE(ndev),
> > GFP_ATOMIC);
> > - if (unlikely(!skb))
> > + if (unlikely(!skb)) {
> > + rcu_read_unlock();
> > goto out;
> > + }
> > skb_reserve(skb, hdr_len + LL_RESERVED_SPACE(ndev));
> > /* FIXME: hold reference to this netdev until life of this skb. */
> > skb->dev = ndev;
> > + rcu_read_unlock();
> > +
> > if (av->network_type == RDMA_NETWORK_IPV4)
> > skb->protocol = htons(ETH_P_IP);
> > else
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