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Wed, 03 Sep 2025 11:19:30 -0700 (PDT) From: Stanislav Fort X-Google-Original-From: Stanislav Fort To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, linux-hams@vger.kernel.org, linux-kernel@vger.kernel.org, security@kernel.org, Stanislav Fort Subject: [PATCH net v3] netrom: linearize and validate lengths in nr_rx_frame() Date: Wed, 3 Sep 2025 21:19:15 +0300 Message-Id: <20250903181915.6359-1-disclosure@aisle.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <20250902112652.26293-1-disclosure@aisle.com> References: <20250902112652.26293-1-disclosure@aisle.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 (>= =3D 21 bytes). - For CONNREQ handling, ensure window (byte 20) and user address (bytes 21-= 27) are present (>=3D 28 bytes). - Maintain existing BPQ extension handling: - NR_CONNACK len =3D=3D 22 implies 1 extra byte (TTL) - NR_CONNREQ len =3D=3D 37 implies 2 extra bytes (timeout) Suggested-by: Eric Dumazet Reported-by: Stanislav Fort Signed-off-by: Stanislav Fort Reviewed-by: Eric Dumazet --- 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 */ =20 + if (skb_linearize(skb)) + return 0; + if (skb->len < NR_NETWORK_LEN + NR_TRANSPORT_LEN) + return 0; + src =3D (ax25_address *)(skb->data + 0); dest =3D (ax25_address *)(skb->data + 7); =20 @@ -927,6 +932,11 @@ int nr_rx_frame(struct sk_buff *skb, struct net_device= *dev) } =20 if (sk !=3D NULL) { + if (frametype =3D=3D 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); =20 @@ -961,10 +971,14 @@ int nr_rx_frame(struct sk_buff *skb, struct net_devic= e *dev) return 0; } =20 - sk =3D 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; =20 user =3D (ax25_address *)(skb->data + 21); =20 + sk =3D nr_find_listener(dest); + if (sk =3D=3D NULL || sk_acceptq_is_full(sk) || (make =3D nr_make_new(sk)) =3D=3D NULL) { nr_transmit_refusal(skb, 0); --=20 2.39.3 (Apple Git-146)