[PATCH] Bluetooth: bnep: fix out-of-bounds reads on short RX/TX frames and control fallthrough

[Hui Peng <benquike@gmail.com>]

Fix multiple out-of-bounds reads in Bluetooth BNEP frame processing:

1. In bnep_rx_frame() and bnep_ctrl_frame() (net/bluetooth/bnep/core.c),
   use pskb_may_pull() to verify the BNEP header, control type byte,
   filter count, and extension headers exist before reading them, and
   return 0 after handling BNEP_CONTROL instead of falling through to
   Ethernet frame submission when no extension headers follow.
2. In bnep_net_xmit() (net/bluetooth/bnep/netdev.c), verify skb->len >=
   ETH_HLEN with pskb_may_pull() before reading the 14-byte Ethernet
   header to prevent an out-of-bounds heap read and infoleak on short
   AF_PACKET TX frames.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Assisted-by: LLM
Signed-off-by: Hui Peng <benquike@gmail.com>
---
diff --git a/net/bluetooth/bnep/core.c b/net/bluetooth/bnep/core.c
index f7d88c33e23e..ad24d2486665 100644
--- a/net/bluetooth/bnep/core.c
+++ b/net/bluetooth/bnep/core.c
@@ -270,9 +270,14 @@ static int bnep_rx_extension(struct bnep_session *s, struct sk_buff *skb)
 
 		BT_DBG("type 0x%x len %u", h->type, h->len);
 
+		if (skb->len < h->len) {
+			err = -EILSEQ;
+			break;
+		}
+
 		switch (h->type & BNEP_TYPE_MASK) {
 		case BNEP_EXT_CONTROL:
-			bnep_rx_control(s, skb->data, skb->len);
+			bnep_rx_control(s, skb->data, h->len);
 			break;
 
 		default:
@@ -373,6 +378,11 @@ static int bnep_rx_frame(struct bnep_session *s, struct sk_buff *skb)
 			goto badframe;
 	}
 
+	if ((type & BNEP_TYPE_MASK) == BNEP_CONTROL) {
+		kfree_skb(skb);
+		return 0;
+	}
+
 	/* Strip 802.1p header */
 	if (ntohs(s->eh.h_proto) == ETH_P_8021Q) {
 		if (!skb_pull(skb, 4))
@@ -451,6 +461,11 @@ static int bnep_tx_frame(struct bnep_session *s, struct sk_buff *skb)
 		goto send;
 	}
 
+	if (skb->len < ETH_HLEN) {
+		kfree_skb(skb);
+		return 0;
+	}
+
 	iv[il++] = (struct kvec) { &type, 1 };
 	len++;
 
diff --git a/net/bluetooth/bnep/netdev.c b/net/bluetooth/bnep/netdev.c
index ee1e39a3daff..b451ef457741 100644
--- a/net/bluetooth/bnep/netdev.c
+++ b/net/bluetooth/bnep/netdev.c
@@ -166,6 +166,12 @@ static netdev_tx_t bnep_net_xmit(struct sk_buff *skb,
 
 	BT_DBG("skb %p, dev %p", skb, dev);
 
+	if (!pskb_may_pull(skb, ETH_HLEN)) {
+		dev->stats.tx_dropped++;
+		kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
 #ifdef CONFIG_BT_BNEP_MC_FILTER
 	if (bnep_net_mc_filter(skb, s)) {
 		kfree_skb(skb);
@@ -218,7 +224,7 @@ void bnep_net_setup(struct net_device *dev)
 	dev->addr_len = ETH_ALEN;
 
 	ether_setup(dev);
-	dev->min_mtu = 0;
+	dev->min_mtu = ETH_MIN_MTU;
 	dev->max_mtu = ETH_MAX_MTU;
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 	dev->netdev_ops = &bnep_netdev_ops;