[B.A.T.M.A.N.] [PATCH 07/14] batman-adv: Make MCAST capability changes atomic

Antonio Quartulli
2015-08-04T16:35:27Z

From: 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()/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>
---
net/batman-adv/multicast.c | 18 ++++++++++--------
net/batman-adv/types.h | 2 +-
2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/net/batman-adv/multicast.c b/net/batman-adv/multicast.c
index 7aa480b..f92473d 100644
--- 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 6f801ef..1eeed18 100644
--- 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,
};

/**
--
2.5.0