[B.A.T.M.A.N.] [PATCHv3 maint 4/5] batman-adv: Make MCAST capability changes atomic

[Linus Lüssing]

Bitwise OR/AND assignments in C aren't guaranteed to be atomic. One
OGM handler might undo the set/clear of a specific bit from another
handler run in between.

Fix this by using the atomic set_bit()/clear_bit() functions.

Fixes: 77ec494490d6 ("batman-adv: Announce new capability via multicast TVLV")
Signed-off-by: Linus Lüssing <linus.luess...@c0d3.blue>
---
 multicast.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/multicast.c b/multicast.c
index 09f2838..00612bf 100644
--- a/multicast.c
+++ b/multicast.c
@@ -684,7 +684,7 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct 
batadv_priv *bat_priv,
            !(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST)) {
                if (orig_initialized)
                        atomic_dec(&bat_priv->mcast.num_disabled);
-               orig->capabilities |= BATADV_ORIG_CAPA_HAS_MCAST;
+               set_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capabilities);
        /* If mcast support is being switched off or if this is an initial
         * OGM without mcast support then increase the disabled mcast
         * node counter.
@@ -693,10 +693,10 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct 
batadv_priv *bat_priv,
                   (orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST ||
                    !orig_initialized)) {
                atomic_inc(&bat_priv->mcast.num_disabled);
-               orig->capabilities &= ~BATADV_ORIG_CAPA_HAS_MCAST;
+               clear_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capabilities);
        }
 
-       orig->capa_initialized |= BATADV_ORIG_CAPA_HAS_MCAST;
+       set_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capa_initialized);
 
        if (orig_mcast_enabled && tvlv_value &&
            (tvlv_value_len >= sizeof(mcast_flags)))
-- 
1.7.10.4