[RTNETLINK]: Hold rtnl_mutex during netlink dump callbacks

Hold rtnl_mutex during the entire netlink dump operation. This allows
to simplify locking in the dump callbacks, since they can now rely on
that no concurrent changes happen.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 2 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 648a7b6d15df..62f5c7f98d17 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -859,6 +859,7 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
         int min_len;
         int family;
         int type;
+        int err;
 
         type = nlh->nlmsg_type;
         if (type > RTM_MAX)
@@ -887,7 +888,10 @@ static int rtnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
                 if (dumpit == NULL)
                         return -EOPNOTSUPP;
 
-                return netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
+                __rtnl_unlock();
+                err = netlink_dump_start(rtnl, skb, nlh, dumpit, NULL);
+                rtnl_lock();
+                return err;
         }
 
         memset(rta_buf, 0, (rtattr_max * sizeof(struct rtattr *)));
@@ -972,7 +976,7 @@ void __init rtnetlink_init(void)
                 panic("rtnetlink_init: cannot allocate rta_buf\n");
 
         rtnl = netlink_kernel_create(NETLINK_ROUTE, RTNLGRP_MAX, rtnetlink_rcv,
-                                     NULL, THIS_MODULE);
+                                     &rtnl_mutex, THIS_MODULE);
         if (rtnl == NULL)
                 panic("rtnetlink_init: cannot initialize rtnetlink\n");
         netlink_set_nonroot(NETLINK_ROUTE, NL_NONROOT_RECV);