linux-kernel - [PATCH 3.16.y-ckt 096/133] batman-adv: Make NC capability changes atomic

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Date:	Wed, 30 Sep 2015 10:50:44 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Linus Lüssing <linus.luessing@...3.blue>,
	Marek Lindner <mareklindner@...mailbox.ch>,
	Antonio Quartulli <antonio@...hcoding.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 096/133] batman-adv: Make NC capability changes atomic

3.16.7-ckt18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: =?UTF-8?q?Linus=20L=C3=BCssing?= <linus.luessing@...3.blue>

commit 4635469f5c617282f18c69643af36cd8c0acf707 upstream.

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: 3f4841ffb336 ("batman-adv: tvlv - add network coding container")
Signed-off-by: Linus Lüssing <linus.luessing@...3.blue>
Signed-off-by: Marek Lindner <mareklindner@...mailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@...hcoding.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 net/batman-adv/network-coding.c | 7 ++++---
 net/batman-adv/types.h          | 2 +-
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index 8d04d174669e..65d19690d8ae 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -15,6 +15,7 @@
  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <linux/bitops.h>
 #include <linux/debugfs.h>
 
 #include "main.h"
@@ -105,9 +106,9 @@ static void batadv_nc_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv,
 					  uint16_t tvlv_value_len)
 {
 	if (flags & BATADV_TVLV_HANDLER_OGM_CIFNOTFND)
-		orig->capabilities &= ~BATADV_ORIG_CAPA_HAS_NC;
+		clear_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);
 	else
-		orig->capabilities |= BATADV_ORIG_CAPA_HAS_NC;
+		set_bit(BATADV_ORIG_CAPA_HAS_NC, &orig->capabilities);
 }
 
 /**
@@ -871,7 +872,7 @@ void batadv_nc_update_nc_node(struct batadv_priv *bat_priv,
 		goto out;
 
 	/* check if orig node is network coding enabled */
-	if (!(orig_node->capabilities & BATADV_ORIG_CAPA_HAS_NC))
+	if (!test_bit(BATADV_ORIG_CAPA_HAS_NC, &orig_node->capabilities))
 		goto out;
 
 	/* accept ogms from 'good' neighbors and single hop neighbors */
diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h
index 3d316c8d340c..1b0b053ae729 100644
--- a/net/batman-adv/types.h
+++ b/net/batman-adv/types.h
@@ -299,7 +299,7 @@ struct batadv_orig_node {
  */
 enum batadv_orig_capabilities {
 	BATADV_ORIG_CAPA_HAS_DAT,
-	BATADV_ORIG_CAPA_HAS_NC = BIT(1),
+	BATADV_ORIG_CAPA_HAS_NC,
 	BATADV_ORIG_CAPA_HAS_TT = BIT(2),
 	BATADV_ORIG_CAPA_HAS_MCAST = BIT(3),
 };
--
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