net: core: neighbour: Process ARP queue later

ARP queue processing unlocks the neighbor lock, which can allow another
thread to asynchronously perform a neighbor update and send an out of order
notification. Therefore this needs to be done after the notification is
sent.

Move it just before the end of the critical section. Since
neigh_update_process_arp_queue() unlocks, it does not form a part of the
critical section anymore but it can benefit from the lock being taken. The
intention is to eventually do the RTNL notification before this call.

This motion crosses a call to neigh_update_is_router(), which should not
influence processing of the ARP queue.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/9ea7159e71430ebdc837ebcc880a76b7e82e52a4.1769012464.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index b6cb127a5b8e18f4d30eb6b7ed887d2c782baeac..3d969f0190a196f42b73d70edc27ae6722584a95 100644 (file)
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -1369,6 +1369,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
                          struct netlink_ext_ack *extack)
 {
        bool gc_update = false, managed_update = false;
+       bool process_arp_queue = false;
        int update_isrouter = 0;
        struct net_device *dev;
        int err, notify = 0;
@@ -1504,12 +1505,17 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
                neigh_suspect(neigh);
 
        if (!(old & NUD_VALID))
-               neigh_update_process_arp_queue(neigh);
+               process_arp_queue = true;
 
 out:
        if (update_isrouter)
                neigh_update_is_router(neigh, flags, &notify);
+
+       if (process_arp_queue)
+               neigh_update_process_arp_queue(neigh);
+
        write_unlock_bh(&neigh->lock);
+
        if (((new ^ old) & NUD_PERMANENT) || gc_update)
                neigh_update_gc_list(neigh);
        if (managed_update)