[PATCH net v3] netrom: linearize and validate lengths in nr_rx_frame()
From: Stanislav Fort <hidden>
Date: 2025-09-03 18:19:32
Also in:
linux-hams, lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Linearize skb and add targeted length checks in nr_rx_frame() to avoid out-of-bounds reads and potential use-after-free when processing malformed NET/ROM frames. - Linearize skb and require at least NR_NETWORK_LEN + NR_TRANSPORT_LEN (20 bytes) before reading network/transport fields. - For existing sockets path, ensure NR_CONNACK includes the window byte (>= 21 bytes). - For CONNREQ handling, ensure window (byte 20) and user address (bytes 21-27) are present (>= 28 bytes). - Maintain existing BPQ extension handling: - NR_CONNACK len == 22 implies 1 extra byte (TTL) - NR_CONNREQ len == 37 implies 2 extra bytes (timeout) Suggested-by: Eric Dumazet <edumazet@google.com> Reported-by: Stanislav Fort <redacted> Signed-off-by: Stanislav Fort <redacted> --- net/netrom/af_netrom.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c
index 3331669d8e33..f0660dd6d3b0 100644
--- a/net/netrom/af_netrom.c
+++ b/net/netrom/af_netrom.c@@ -885,6 +885,11 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev) * skb->data points to the netrom frame start */ + if (skb_linearize(skb)) + return 0; + if (skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN) + return 0; + src = (ax25_address *)(skb->data + 0); dest = (ax25_address *)(skb->data + 7);
@@ -927,6 +932,11 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev) } if (sk != NULL) { + if (frametype == NR_CONNACK && + skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1) { + sock_put(sk); + return 0; + } bh_lock_sock(sk); skb_reset_transport_header(skb);
@@ -961,10 +971,14 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device *dev) return 0; } - sk = nr_find_listener(dest); + /* Need window (byte 20) and user address (bytes 21-27) */ + if (skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN + 1 + AX25_ADDR_LEN) + return 0; user = (ax25_address *)(skb->data + 21); + sk = nr_find_listener(dest); + if (sk == NULL || sk_acceptq_is_full(sk) || (make = nr_make_new(sk)) == NULL) { nr_transmit_refusal(skb, 0);
--
2.39.3 (Apple Git-146)