[B.A.T.M.A.N.] [PATCH v2 0/5] batman-adv: Missing list checks for *list_add*

[B.A.T.M.A.N.] [PATCH v2 0/5] batman-adv: Missing list checks for *list_add*

[Sven Eckelmann]

Hi,

Marek reviewed the the previous version of the patcheset [0] and requested
some changes for patch 1 and 3.

* patch 1:

  - added kerneldoc about the locking requirements

* patch 3

  - changed batadv_softif_create_vlan to handle problems in
    batadv_sysfs_add_vlan as fatal error

Kind regards,
        Sven

[0] https://patchwork.open-mesh.org/project/b.a.t.m.a.n./list/?series=150&submitter=&state=*&q=&archive=both&delegate=
[1] https://www.open-mesh.org/issues/235
[2] https://www.open-mesh.org/issues/236
[3] https://www.open-mesh.org/issues/237
[4] https://www.open-mesh.org/issues/238
[5] https://www.open-mesh.org/issues/239
[6] https://www.open-mesh.org/issues/240
[7] https://www.open-mesh.org/issues/241
[8] https://patchwork.open-mesh.org/patch/4919/

 net/batman-adv/gateway_client.c    | 11 +++++++++--
 net/batman-adv/network-coding.c    | 27 +++++++++++++++------------
 net/batman-adv/soft-interface.c    | 25 ++++++++++++++++++-------
 net/batman-adv/translation-table.c |  6 ++++--
 net/batman-adv/tvlv.c              |  8 ++++++--
 5 files changed, 52 insertions(+), 25 deletions(-)

-- 
2.11.0

[B.A.T.M.A.N.] [PATCH v2 1/5] batman-adv: Prevent duplicated gateway_node entry

[Sven Eckelmann]

The function batadv_gw_node_add is responsible for adding new gw_node to
the gateway_list. It is expecting that the caller already checked that
there is not already an entry with the same key or not.

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: bc3538cabac5 ("batman-adv: adding gateway functionality")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Marek Lindner <mareklindner@neomailbox.ch>
---
v2:
* added kerneldoc about the locking requirements

 net/batman-adv/gateway_client.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c
index 8b198ee7..140c61a3 100644
--- a/net/batman-adv/gateway_client.c
+++ b/net/batman-adv/gateway_client.c
@@ -32,6 +32,7 @@
 #include <linux/kernel.h>
 #include <linux/kref.h>
 #include <linux/list.h>
+#include <linux/lockdep.h>
 #include <linux/netdevice.h>
 #include <linux/netlink.h>
 #include <linux/rculist.h>
@@ -348,6 +349,9 @@ void batadv_gw_check_election(struct batadv_priv *bat_priv,
  * @bat_priv: the bat priv with all the soft interface information
  * @orig_node: originator announcing gateway capabilities
  * @gateway: announced bandwidth information
+ *
+ * Has to be called with the appropriate locks being acquired
+ * (gw.list_lock).
  */
 static void batadv_gw_node_add(struct batadv_priv *bat_priv,
 			       struct batadv_orig_node *orig_node,
@@ -355,6 +359,8 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv,
 {
 	struct batadv_gw_node *gw_node;
 
+	lockdep_assert_held(&bat_priv->gw.list_lock);
+
 	if (gateway->bandwidth_down == 0)
 		return;
 
@@ -369,10 +375,8 @@ static void batadv_gw_node_add(struct batadv_priv *bat_priv,
 	gw_node->bandwidth_down = ntohl(gateway->bandwidth_down);
 	gw_node->bandwidth_up = ntohl(gateway->bandwidth_up);
 
-	spin_lock_bh(&bat_priv->gw.list_lock);
 	kref_get(&gw_node->refcount);
 	hlist_add_head_rcu(&gw_node->list, &bat_priv->gw.gateway_list);
-	spin_unlock_bh(&bat_priv->gw.list_lock);
 
 	batadv_dbg(BATADV_DBG_BATMAN, bat_priv,
 		   "Found new gateway %pM -> gw bandwidth: %u.%u/%u.%u MBit\n",
@@ -428,11 +432,14 @@ void batadv_gw_node_update(struct batadv_priv *bat_priv,
 {
 	struct batadv_gw_node *gw_node, *curr_gw = NULL;
 
+	spin_lock_bh(&bat_priv->gw.list_lock);
 	gw_node = batadv_gw_node_get(bat_priv, orig_node);
 	if (!gw_node) {
 		batadv_gw_node_add(bat_priv, orig_node, gateway);
+		spin_unlock_bh(&bat_priv->gw.list_lock);
 		goto out;
 	}
+	spin_unlock_bh(&bat_priv->gw.list_lock);
 
 	if (gw_node->bandwidth_down == ntohl(gateway->bandwidth_down) &&
 	    gw_node->bandwidth_up == ntohl(gateway->bandwidth_up))
-- 
2.11.0

[B.A.T.M.A.N.] [PATCH v2 2/5] batman-adv: Prevent duplicated nc_node entry

[Sven Eckelmann]

The function batadv_nc_get_nc_node is responsible for adding new nc_nodes
to the in_coding_list and out_coding_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: 3ed7ada3f0bb ("batman-adv: network coding - detect coding nodes and remove these after timeout")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Marek Lindner <mareklindner@neomailbox.ch>
---
 net/batman-adv/network-coding.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/net/batman-adv/network-coding.c b/net/batman-adv/network-coding.c
index c3578444..34caf129 100644
--- a/net/batman-adv/network-coding.c
+++ b/net/batman-adv/network-coding.c
@@ -854,16 +854,27 @@ batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
 	spinlock_t *lock; /* Used to lock list selected by "int in_coding" */
 	struct list_head *list;
 
+	/* Select ingoing or outgoing coding node */
+	if (in_coding) {
+		lock = &orig_neigh_node->in_coding_list_lock;
+		list = &orig_neigh_node->in_coding_list;
+	} else {
+		lock = &orig_neigh_node->out_coding_list_lock;
+		list = &orig_neigh_node->out_coding_list;
+	}
+
+	spin_lock_bh(lock);
+
 	/* Check if nc_node is already added */
 	nc_node = batadv_nc_find_nc_node(orig_node, orig_neigh_node, in_coding);
 
 	/* Node found */
 	if (nc_node)
-		return nc_node;
+		goto unlock;
 
 	nc_node = kzalloc(sizeof(*nc_node), GFP_ATOMIC);
 	if (!nc_node)
-		return NULL;
+		goto unlock;
 
 	/* Initialize nc_node */
 	INIT_LIST_HEAD(&nc_node->list);
@@ -872,22 +883,14 @@ batadv_nc_get_nc_node(struct batadv_priv *bat_priv,
 	kref_get(&orig_neigh_node->refcount);
 	nc_node->orig_node = orig_neigh_node;
 
-	/* Select ingoing or outgoing coding node */
-	if (in_coding) {
-		lock = &orig_neigh_node->in_coding_list_lock;
-		list = &orig_neigh_node->in_coding_list;
-	} else {
-		lock = &orig_neigh_node->out_coding_list_lock;
-		list = &orig_neigh_node->out_coding_list;
-	}
-
 	batadv_dbg(BATADV_DBG_NC, bat_priv, "Adding nc_node %pM -> %pM\n",
 		   nc_node->addr, nc_node->orig_node->orig);
 
 	/* Add nc_node to orig_node */
-	spin_lock_bh(lock);
 	kref_get(&nc_node->refcount);
 	list_add_tail_rcu(&nc_node->list, list);
+
+unlock:
 	spin_unlock_bh(lock);
 
 	return nc_node;
-- 
2.11.0

[B.A.T.M.A.N.] [PATCH v2 3/5] batman-adv: Prevent duplicated softif_vlan entry

[Sven Eckelmann]

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: 952cebb57518 ("batman-adv: add per VLAN interface attribute framework")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
v2:
* changed batadv_softif_create_vlan to handle problems in
  batadv_sysfs_add_vlan as fatal error

 net/batman-adv/soft-interface.c | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 1485263a..626ddca3 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -574,15 +574,20 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 	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_put(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;
@@ -590,17 +595,23 @@ int batadv_softif_create_vlan(struct batadv_priv *bat_priv, unsigned short vid)
 
 	atomic_set(&vlan->ap_isolation, 0);
 
+	kref_get(&vlan->refcount);
+	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 function */
+		batadv_softif_vlan_put(vlan);
+
+		/* ref for the list */
+		batadv_softif_vlan_put(vlan);
 		return err;
 	}
 
-	spin_lock_bh(&bat_priv->softif_vlan_list_lock);
-	kref_get(&vlan->refcount);
-	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
 	 */
-- 
2.11.0

[B.A.T.M.A.N.] [PATCH v2 4/5] batman-adv: Prevent duplicated global TT entry

[Sven Eckelmann]

The function batadv_tt_global_orig_entry_add is responsible for adding new
tt_orig_list_entry to the orig_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: c5eb5bb30321 ("batman-adv: add reference counting for type batadv_tt_orig_list_entry")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Marek Lindner <mareklindner@neomailbox.ch>
---
 net/batman-adv/translation-table.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c
index 12a2b7d2..d21624c4 100644
--- a/net/batman-adv/translation-table.c
+++ b/net/batman-adv/translation-table.c
@@ -1613,6 +1613,8 @@ batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 {
 	struct batadv_tt_orig_list_entry *orig_entry;
 
+	spin_lock_bh(&tt_global->list_lock);
+
 	orig_entry = batadv_tt_global_orig_entry_find(tt_global, orig_node);
 	if (orig_entry) {
 		/* refresh the ttvn: the current value could be a bogus one that
@@ -1635,11 +1637,9 @@ batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 	orig_entry->flags = flags;
 	kref_init(&orig_entry->refcount);
 
-	spin_lock_bh(&tt_global->list_lock);
 	kref_get(&orig_entry->refcount);
 	hlist_add_head_rcu(&orig_entry->list,
 			   &tt_global->orig_list);
-	spin_unlock_bh(&tt_global->list_lock);
 	atomic_inc(&tt_global->orig_list_count);
 
 sync_flags:
@@ -1647,6 +1647,8 @@ batadv_tt_global_orig_entry_add(struct batadv_tt_global_entry *tt_global,
 out:
 	if (orig_entry)
 		batadv_tt_orig_list_entry_put(orig_entry);
+
+	spin_unlock_bh(&tt_global->list_lock);
 }
 
 /**
-- 
2.11.0

[B.A.T.M.A.N.] [PATCH v2 5/5] batman-adv: Prevent duplicated tvlv handler

[Sven Eckelmann]

The function batadv_tvlv_handler_register is responsible for adding new
tvlv_handler to the handler_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: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Acked-by: Marek Lindner <mareklindner@neomailbox.ch>
---
 net/batman-adv/tvlv.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/tvlv.c b/net/batman-adv/tvlv.c
index a6374582..40e69c93 100644
--- a/net/batman-adv/tvlv.c
+++ b/net/batman-adv/tvlv.c
@@ -529,15 +529,20 @@ void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
 {
 	struct batadv_tvlv_handler *tvlv_handler;
 
+	spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
+
 	tvlv_handler = batadv_tvlv_handler_get(bat_priv, type, version);
 	if (tvlv_handler) {
+		spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
 		batadv_tvlv_handler_put(tvlv_handler);
 		return;
 	}
 
 	tvlv_handler = kzalloc(sizeof(*tvlv_handler), GFP_ATOMIC);
-	if (!tvlv_handler)
+	if (!tvlv_handler) {
+		spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
 		return;
+	}
 
 	tvlv_handler->ogm_handler = optr;
 	tvlv_handler->unicast_handler = uptr;
@@ -547,7 +552,6 @@ void batadv_tvlv_handler_register(struct batadv_priv *bat_priv,
 	kref_init(&tvlv_handler->refcount);
 	INIT_HLIST_NODE(&tvlv_handler->list);
 
-	spin_lock_bh(&bat_priv->tvlv.handler_list_lock);
 	kref_get(&tvlv_handler->refcount);
 	hlist_add_head_rcu(&tvlv_handler->list, &bat_priv->tvlv.handler_list);
 	spin_unlock_bh(&bat_priv->tvlv.handler_list_lock);
-- 
2.11.0

Re: [B.A.T.M.A.N.] [PATCH v2 0/5] batman-adv: Missing list checks for *list_add*

[Sven Eckelmann]

[-- Attachment #1: Type: text/plain, Size: 730 bytes --]

On Donnerstag, 6. September 2018 14:35:23 CEST Sven Eckelmann wrote:
> Hi,
> 
> Marek reviewed the the previous version of the patcheset [0] and requested
> some changes for patch 1 and 3.
[...]

Added as 848be9859b01..acabad79e017 [1,2,3,4,5]

Kind regards,
	Sven

[1] https://git.open-mesh.org/batman-adv.git/commit/69b3ca714eba608fe79a51ccd89ce7050ee0b770
[2] https://git.open-mesh.org/batman-adv.git/commit/bab8447ad1850b25188f9652c0c52f8e58acd656
[3] https://git.open-mesh.org/batman-adv.git/commit/023d3f64207e8b6a6e6d0718d98e239c5545ef0c
[4] https://git.open-mesh.org/batman-adv.git/commit/79097255a1a3e1bd1949be309af941181fbc7b36
[5] https://git.open-mesh.org/batman-adv.git/commit/acabad79e01740525cf4ff8ce6e9a210b683d420

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