Patch "batman-adv: Prevent duplicated softif_vlan entry" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    batman-adv: Prevent duplicated softif_vlan entry

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     batman-adv-prevent-duplicated-softif_vlan-entry.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From foo@baz Tue Nov 23 01:39:02 PM CET 2021
From: Sven Eckelmann <sven@narfation.org>
Date: Sat, 20 Nov 2021 13:39:31 +0100
Subject: batman-adv: Prevent duplicated softif_vlan entry
To: stable@vger.kernel.org
Cc: b.a.t.m.a.n@lists.open-mesh.org, Sven Eckelmann <sven@narfation.org>, Simon Wunderlich <sw@simonwunderlich.de>
Message-ID: <20211120123939.260723-4-sven@narfation.org>

From: Sven Eckelmann <sven@narfation.org>

commit 94cb82f594ed86be303398d6dfc7640a6f1d45d4 upstream.

The function batadv_softif_vlan_get is responsible for adding new
softif_vlan to the softif_vlan_list. It first checks whether the entry
already is in the list or not. If it is, then the creation of a new entry
is aborted.

But the lock for the list is only held when the list is really modified.
This could lead to duplicated entries because another context could create
an entry with the same key between the check and the list manipulation.

The check and the manipulation of the list must therefore be in the same
locked code section.

Fixes: 5d2c05b21337 ("batman-adv: add per VLAN interface attribute framework")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
[ bp: 4.4 backport: switch back to atomic_t based reference counting. ]
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/batman-adv/soft-interface.c |   20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -539,15 +539,20 @@ int batadv_softif_create_vlan(struct bat
 	struct batadv_softif_vlan *vlan;
 	int err;
 
+	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
+
 	vlan = batadv_softif_vlan_get(bat_priv, vid);
 	if (vlan) {
 		batadv_softif_vlan_free_ref(vlan);
+		spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 		return -EEXIST;
 	}
 
 	vlan = kzalloc(sizeof(*vlan), GFP_ATOMIC);
-	if (!vlan)
+	if (!vlan) {
+		spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
 		return -ENOMEM;
+	}
 
 	vlan->bat_priv = bat_priv;
 	vlan->vid = vid;
@@ -555,16 +560,19 @@ int batadv_softif_create_vlan(struct bat
 
 	atomic_set(&vlan->ap_isolation, 0);
 
+	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
+	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
+
+	/* batadv_sysfs_add_vlan cannot be in the spinlock section due to the
+	 * sleeping behavior of the sysfs functions and the fs_reclaim lock
+	 */
 	err = batadv_sysfs_add_vlan(bat_priv->soft_iface, vlan);
 	if (err) {
-		kfree(vlan);
+		/* ref for the list */
+		batadv_softif_vlan_free_ref(vlan);
 		return err;
 	}
 
-	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
-	hlist_add_head_rcu(&vlan->list, &bat_priv->softif_vlan_list);
-	spin_unlock_bh(&bat_priv->softif_vlan_list_lock);
-
 	/* add a new TT local entry. This one will be marked with the NOPURGE
 	 * flag
 	 */


Patches currently in stable-queue which might be from sven@narfation.org are

queue-4.4/batman-adv-consider-fragmentation-for-needed_headroom.patch
queue-4.4/ath9k-fix-potential-interrupt-storm-on-queue-reset.patch
queue-4.4/batman-adv-set-.owner-to-this_module.patch
queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-from-bla-backbone-to-mesh.patch
queue-4.4/batman-adv-fix-multicast-tt-issues-with-bogus-roam-flags.patch
queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-in-bla-backbone-from-lan.patch
queue-4.4/batman-adv-reserve-needed_-room-for-fragments.patch
queue-4.4/net-batman-adv-fix-error-handling.patch
queue-4.4/batman-adv-keep-fragments-equally-sized.patch
queue-4.4/batman-adv-avoid-warn_on-timing-related-checks.patch
queue-4.4/batman-adv-prevent-duplicated-softif_vlan-entry.patch
queue-4.4/batman-adv-don-t-always-reallocate-the-fragmentation-skb-head.patch
queue-4.4/batman-adv-mcast-fix-duplicate-mcast-packets-in-bla-backbone-from-mesh.patch