batman-adv: Make MCAST capability changes atomic

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()/test_bit() functions.

Fixes: 60432d756cf0 ("batman-adv: Announce new capability via multicast TVLV")
Signed-off-by: Linus Lüssing <linus.luessing@c0d3.blue>
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 7aa480b7edd0d5fa56a7d88aa09c9db5da48068a..8f1ec21bf2d073697033d9bf70cfe84ccccc29ee 100644 (file)
--- a/net/batman-adv/multicast.c
+++ b/net/batman-adv/multicast.c
@@ -19,6 +19,7 @@
 #include "main.h"
 
 #include <linux/atomic.h>
+#include <linux/bitops.h>
 #include <linux/byteorder/generic.h>
 #include <linux/errno.h>
 #include <linux/etherdevice.h>
@@ -697,29 +698,30 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
        uint8_t mcast_flags = BATADV_NO_FLAGS;
        bool orig_initialized;
 
-       orig_initialized = orig->capa_initialized & BATADV_ORIG_CAPA_HAS_MCAST;
+       orig_initialized = test_bit(BATADV_ORIG_CAPA_HAS_MCAST,
+                                   &orig->capa_initialized);
 
        /* If mcast support is turned on decrease the disabled mcast node
         * counter only if we had increased it for this node before. If this
         * is a completely new orig_node no need to decrease the counter.
         */
        if (orig_mcast_enabled &&
-           !(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST)) {
+           !test_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capabilities)) {
                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.
         */
        } else if (!orig_mcast_enabled &&
-                  (orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST ||
+                  (test_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capabilities) ||
                    !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)))
@@ -763,8 +765,8 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig)
 {
        struct batadv_priv *bat_priv = orig->bat_priv;
 
-       if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST) &&
-           orig->capa_initialized & BATADV_ORIG_CAPA_HAS_MCAST)
+       if (!test_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capabilities) &&
+           test_bit(BATADV_ORIG_CAPA_HAS_MCAST, &orig->capa_initialized))
                atomic_dec(&bat_priv->mcast.num_disabled);
 
        batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);

diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 6f801efc3ae2828e5275d922dc86ae6a41a745fb..1eeed1847bc73dd0cdc8942f7d136b0bf87bf8f4 100644 (file)
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -316,7 +316,7 @@ enum batadv_orig_capabilities {
        BATADV_ORIG_CAPA_HAS_DAT,
        BATADV_ORIG_CAPA_HAS_NC,
        BATADV_ORIG_CAPA_HAS_TT,
-       BATADV_ORIG_CAPA_HAS_MCAST = BIT(3),
+       BATADV_ORIG_CAPA_HAS_MCAST,
 };
 
 /**