[B.A.T.M.A.N.] [PATCHv2 maint 4/5] batman-adv: Make MCAST capability changes atomic

["Linus Lüssing" <linus.luessing@c0d3.blue>]

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.luessing@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