[PATCH net-next] scsi: libcxgbi: fib6_ino reference in rt6_info is rcu protected

[dsahern]

From: David Ahern <dsah...@gmail.com>

The fib6_info reference in rt6_info is rcu protected. Add a helper
to extract prefsrc from and update cxgbi_check_route6 to use it.

Fixes: 0153167aebd0 ("net/ipv6: Remove rt6i_prefsrc")
Reported-by: kbuild test robot <l...@intel.com>
Signed-off-by: David Ahern <dsah...@gmail.com>
---
 drivers/scsi/cxgbi/libcxgbi.c |  5 ++---
 include/net/ip6_fib.h         | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/cxgbi/libcxgbi.c b/drivers/scsi/cxgbi/libcxgbi.c
index 6b3ea50c594e..75f876409fb9 100644
--- a/drivers/scsi/cxgbi/libcxgbi.c
+++ b/drivers/scsi/cxgbi/libcxgbi.c
@@ -784,7 +784,8 @@ cxgbi_check_route6(struct sockaddr *dst_addr, int ifindex)
        csk->mtu = mtu;
        csk->dst = dst;
 
-       if (!rt->from || ipv6_addr_any(&rt->from->fib6_prefsrc.addr)) {
+       rt6_get_prefsrc(rt, &pref_saddr);
+       if (ipv6_addr_any(&pref_saddr)) {
                struct inet6_dev *idev = ip6_dst_idev((struct dst_entry *)rt);
 
                err = ipv6_dev_get_saddr(&init_net, idev ? idev->dev : NULL,
@@ -794,8 +795,6 @@ cxgbi_check_route6(struct sockaddr *dst_addr, int ifindex)
                                &daddr6->sin6_addr);
                        goto rel_rt;
                }
-       } else {
-               pref_saddr = rt->from->fib6_prefsrc.addr;
        }
 
        csk->csk_family = AF_INET6;
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index c7496663f99a..f06e968f1992 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -412,6 +412,25 @@ int fib6_add(struct fib6_node *root, struct fib6_info *rt,
             struct nl_info *info, struct netlink_ext_ack *extack);
 int fib6_del(struct fib6_info *rt, struct nl_info *info);
 
+static inline
+void rt6_get_prefsrc(const struct rt6_info *rt, struct in6_addr *addr)
+{
+       const struct fib6_info *from;
+
+       rcu_read_lock();
+
+       from = rcu_dereference(rt->from);
+       if (from) {
+               *addr = from->fib6_prefsrc.addr;
+       } else {
+               struct in6_addr in6_zero = {};
+
+               *addr = in6_zero;
+       }
+
+       rcu_read_unlock();
+}
+
 static inline struct net_device *fib6_info_nh_dev(const struct fib6_info *f6i)
 {
        return f6i->fib6_nh.nh_dev;
-- 
2.11.0