[PATCH net] bridge: Fix VLAN reference count problem

When a VLAN is added on a port, a reference is taken on the
corresponding master VLAN entry. If it does not already exist, then it
is created and a reference taken.

However, in the second case a reference is not really taken when
CONFIG_REFCOUNT_FULL is enabled as refcount_inc() is replaced by
refcount_inc_not_zero().

Fix this by using refcount_set() on a newly created master VLAN entry.

Fixes: 251277598596 ("net, bridge: convert net_bridge_vlan.refcnt from atomic_t to refcount_t")
Signed-off-by: Ido Schimmel <redacted>
---
 net/bridge/br_vlan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 51935270c651..9896f4975353 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c

@@ -168,6 +168,8 @@ static struct net_bridge_vlan *br_vlan_get_master(struct net_bridge *br, u16 vid
 		masterv = br_vlan_find(vg, vid);
 		if (WARN_ON(!masterv))
 			return NULL;
+		refcount_set(&masterv->refcnt, 1);
+		return masterv;
 	}
 	refcount_inc(&masterv->refcnt);
 

-- 
2.14.3

On 25/02/18 21:59, Ido Schimmel wrote:

Good catch,

Acked-by: Nikolay Aleksandrov <redacted>

From: Ido Schimmel <redacted>
Date: Sun, 25 Feb 2018 21:59:06 +0200

When a VLAN is added on a port, a reference is taken on the
corresponding master VLAN entry. If it does not already exist, then it
is created and a reference taken.

However, in the second case a reference is not really taken when
CONFIG_REFCOUNT_FULL is enabled as refcount_inc() is replaced by
refcount_inc_not_zero().

Fix this by using refcount_set() on a newly created master VLAN entry.

Fixes: 251277598596 ("net, bridge: convert net_bridge_vlan.refcnt from atomic_t to refcount_t")
Signed-off-by: Ido Schimmel <redacted>

Applied and queued up for -stable, thanks!