[PATCH batadv v3 3/4] batman-adv: tvlv: abort OGM send on tvlv append failure

batadv_tvlv_container_ogm_append() could fail in two ways: a memory
allocation failure when resizing the packet buffer, or the tvlv data
exceeding U16_MAX bytes. In both cases the function previously returned the
old (now stale) tvlv_value_len rather than signalling an error, causing the
OGM/OGM2 send path to transmit a packet whose TVLV length field no longer
matched the actual buffer contents. And because it also didn't fill in the
new TVLV data, sending either uninitialized or corrupted data on the wire.

All errors in batadv_tvlv_container_ogm_append() must be forwarded to the
caller. And the caller must abort the send of the OGM(2).

Fixes: 0b6aa0d43767 ("batman-adv: tvlv - basic infrastructure")
Signed-off-by: Sven Eckelmann <[email protected]>
---
 net/batman-adv/bat_iv_ogm.c | 11 ++++++++---
 net/batman-adv/bat_v_ogm.c  | 26 ++++++++++++++------------
 net/batman-adv/tvlv.c       | 21 +++++++++++++++------
 net/batman-adv/tvlv.h       |  2 +-
 4 files changed, 38 insertions(+), 22 deletions(-)

diff --git a/net/batman-adv/bat_iv_ogm.c b/net/batman-adv/bat_iv_ogm.c
index 74ef7dc2..8889d465 100644
--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -790,6 +790,7 @@ static void batadv_iv_ogm_schedule_buff(struct batadv_hard_iface *hard_iface)
 	u32 seqno;
 	u16 tvlv_len = 0;
 	unsigned long send_time;
+	int ret;
 
 	lockdep_assert_held(&hard_iface->bat_iv.ogm_buff_mutex);
 
@@ -813,9 +814,13 @@ static void batadv_iv_ogm_schedule_buff(struct batadv_hard_iface *hard_iface)
 		 * appended as it may alter the tt tvlv container
 		 */
 		batadv_tt_local_commit_changes(bat_priv);
-		tvlv_len = batadv_tvlv_container_ogm_append(bat_priv, ogm_buff,
-							    ogm_buff_len,
-							    BATADV_OGM_HLEN);
+		ret = batadv_tvlv_container_ogm_append(bat_priv, ogm_buff,
+						       ogm_buff_len,
+						       BATADV_OGM_HLEN);
+		if (ret < 0)
+			goto out;
+
+		tvlv_len = ret;
 	}
 
 	batadv_ogm_packet = (struct batadv_ogm_packet *)(*ogm_buff);
diff --git a/net/batman-adv/bat_v_ogm.c b/net/batman-adv/bat_v_ogm.c
index e955b494..d66ca77b 100644
--- a/net/batman-adv/bat_v_ogm.c
+++ b/net/batman-adv/bat_v_ogm.c
@@ -269,10 +269,10 @@ static void batadv_v_ogm_send_meshif(struct batadv_priv *bat_priv)
 	struct batadv_hard_iface *hard_iface;
 	struct batadv_ogm2_packet *ogm_packet;
 	struct sk_buff *skb, *skb_tmp;
-	unsigned char *ogm_buff;
+	unsigned char **ogm_buff;
 	struct list_head *iter;
-	int ogm_buff_len;
-	u16 tvlv_len = 0;
+	int *ogm_buff_len;
+	u16 tvlv_len;
 	int ret;
 
 	lockdep_assert_held(&bat_priv->bat_v.ogm_buff_mutex);
@@ -280,25 +280,27 @@ static void batadv_v_ogm_send_meshif(struct batadv_priv *bat_priv)
 	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
 		goto out;
 
-	ogm_buff = bat_priv->bat_v.ogm_buff;
-	ogm_buff_len = bat_priv->bat_v.ogm_buff_len;
+	ogm_buff = &bat_priv->bat_v.ogm_buff;
+	ogm_buff_len = &bat_priv->bat_v.ogm_buff_len;
+
 	/* tt changes have to be committed before the tvlv data is
 	 * appended as it may alter the tt tvlv container
 	 */
 	batadv_tt_local_commit_changes(bat_priv);
-	tvlv_len = batadv_tvlv_container_ogm_append(bat_priv, &ogm_buff,
-						    &ogm_buff_len,
-						    BATADV_OGM2_HLEN);
+	ret = batadv_tvlv_container_ogm_append(bat_priv, ogm_buff,
+					       ogm_buff_len,
+					       BATADV_OGM2_HLEN);
+	if (ret < 0)
+		goto reschedule;
 
-	bat_priv->bat_v.ogm_buff = ogm_buff;
-	bat_priv->bat_v.ogm_buff_len = ogm_buff_len;
+	tvlv_len = ret;
 
-	skb = netdev_alloc_skb_ip_align(NULL, ETH_HLEN + ogm_buff_len);
+	skb = netdev_alloc_skb_ip_align(NULL, ETH_HLEN + *ogm_buff_len);
 	if (!skb)
 		goto reschedule;
 
 	skb_reserve(skb, ETH_HLEN);
-	skb_put_data(skb, ogm_buff, ogm_buff_len);
+	skb_put_data(skb, *ogm_buff, *ogm_buff_len);
 
 	ogm_packet = (struct batadv_ogm2_packet *)skb->data;
 	ogm_packet->seqno = htonl(atomic_read(&bat_priv->bat_v.ogm_seqno));
diff --git a/net/batman-adv/tvlv.c b/net/batman-adv/tvlv.c
index 4e2a9ec7..cc6ac580 100644
--- a/net/batman-adv/tvlv.c
+++ b/net/batman-adv/tvlv.c
@@ -8,6 +8,7 @@
 
 #include <linux/byteorder/generic.h>
 #include <linux/container_of.h>
+#include <linux/errno.h>
 #include <linux/etherdevice.h>
 #include <linux/gfp.h>
 #include <linux/if_ether.h>
@@ -307,9 +308,10 @@ static bool batadv_tvlv_realloc_packet_buff(unsigned char **packet_buff,
  * The ogm packet might be enlarged or shrunk depending on the current size
  * and the size of the to-be-appended tvlv containers.
  *
- * Return: size of all appended tvlv containers in bytes.
+ * Return: size of all appended tvlv containers in bytes (max U16_MAX), negative
+ *  if operation failed
  */
-u16 batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
+int batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 				     unsigned char **packet_buff,
 				     int *packet_buff_len, int packet_min_len)
 {
@@ -317,18 +319,24 @@ u16 batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 	struct batadv_tvlv_hdr *tvlv_hdr;
 	size_t tvlv_value_len;
 	void *tvlv_value;
+	int tvlv_len_ret;
 	bool ret;
 
 	spin_lock_bh(&bat_priv->tvlv.container_list_lock);
 	tvlv_value_len = batadv_tvlv_container_list_size(bat_priv);
-	if (tvlv_value_len > U16_MAX)
+	if (tvlv_value_len > U16_MAX) {
+		tvlv_len_ret = -E2BIG;
 		goto end;
+	}
 
 	ret = batadv_tvlv_realloc_packet_buff(packet_buff, packet_buff_len,
 					      packet_min_len, tvlv_value_len);
-
-	if (!ret)
+	if (!ret) {
+		tvlv_len_ret = -ENOMEM;
 		goto end;
+	}
+
+	tvlv_len_ret = tvlv_value_len;
 
 	if (!tvlv_value_len)
 		goto end;
@@ -347,7 +355,8 @@ u16 batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 
 end:
 	spin_unlock_bh(&bat_priv->tvlv.container_list_lock);
-	return tvlv_value_len;
+
+	return tvlv_len_ret;
 }
 
 /**
diff --git a/net/batman-adv/tvlv.h b/net/batman-adv/tvlv.h
index e5697230..f96f6b3f 100644
--- a/net/batman-adv/tvlv.h
+++ b/net/batman-adv/tvlv.h
@@ -16,7 +16,7 @@
 void batadv_tvlv_container_register(struct batadv_priv *bat_priv,
 				    u8 type, u8 version,
 				    void *tvlv_value, u16 tvlv_value_len);
-u16 batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
+int batadv_tvlv_container_ogm_append(struct batadv_priv *bat_priv,
 				     unsigned char **packet_buff,
 				     int *packet_buff_len, int packet_min_len);
 void batadv_tvlv_ogm_receive(struct batadv_priv *bat_priv,

-- 
2.47.3