From daf23014e5d975e72ea9c02b5160d3fcf070ea47 Mon Sep 17 00:00:00 2001 From: Michael Bommarito Date: Tue, 21 Apr 2026 13:08:45 -0400 Subject: [PATCH] Bluetooth: virtio_bt: validate rx pkt_type header length virtbt_rx_handle() reads the leading pkt_type byte from the RX skb and forwards the remainder to hci_recv_frame() for every event/ACL/SCO/ISO type, without checking that the remaining payload is at least the fixed HCI header for that type. After the preceding patch bounds the backend-supplied used.len to [1, VIRTBT_RX_BUF_SIZE], a one-byte completion still reaches hci_recv_frame() with skb->len already pulled to 0. If the byte happened to be HCI_ACLDATA_PKT, the ACL-vs-ISO classification fast-path in hci_dev_classify_pkt_type() dereferences hci_acl_hdr(skb)->handle whenever the HCI device has an active CIS_LINK, BIS_LINK, or PA_LINK connection, reading two bytes of uninitialized RX-buffer data. The same hazard exists for every packet type the driver accepts because none of the switch cases in virtbt_rx_handle() check skb->len against the per-type minimum HCI header size before handing the frame to the core. After stripping pkt_type, require skb->len to cover the fixed header size for the selected type (event 2, ACL 4, SCO 3, ISO 4) before calling hci_recv_frame(); drop ratelimited otherwise. Unknown pkt_type values still take the original kfree_skb() default path. Use bt_dev_err_ratelimited() because both the length and pkt_type values come from an untrusted backend that can otherwise flood the kernel log. Fixes: 160fbcf3bfb9 ("Bluetooth: virtio_bt: Use skb_put to set length") Cc: stable@vger.kernel.org Cc: Soenke Huster Signed-off-by: Michael Bommarito Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Luiz Augusto von Dentz --- drivers/bluetooth/virtio_bt.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/drivers/bluetooth/virtio_bt.c b/drivers/bluetooth/virtio_bt.c index 2c5c39356a1c..140ab55c9fc5 100644 --- a/drivers/bluetooth/virtio_bt.c +++ b/drivers/bluetooth/virtio_bt.c @@ -198,6 +198,7 @@ static int virtbt_shutdown_generic(struct hci_dev *hdev) static void virtbt_rx_handle(struct virtio_bluetooth *vbt, struct sk_buff *skb) { + size_t min_hdr; __u8 pkt_type; pkt_type = *((__u8 *) skb->data); @@ -205,16 +206,32 @@ static void virtbt_rx_handle(struct virtio_bluetooth *vbt, struct sk_buff *skb) switch (pkt_type) { case HCI_EVENT_PKT: + min_hdr = sizeof(struct hci_event_hdr); + break; case HCI_ACLDATA_PKT: + min_hdr = sizeof(struct hci_acl_hdr); + break; case HCI_SCODATA_PKT: + min_hdr = sizeof(struct hci_sco_hdr); + break; case HCI_ISODATA_PKT: - hci_skb_pkt_type(skb) = pkt_type; - hci_recv_frame(vbt->hdev, skb); + min_hdr = sizeof(struct hci_iso_hdr); break; default: kfree_skb(skb); - break; + return; } + + if (skb->len < min_hdr) { + bt_dev_err_ratelimited(vbt->hdev, + "rx pkt_type 0x%02x payload %u < hdr %zu\n", + pkt_type, skb->len, min_hdr); + kfree_skb(skb); + return; + } + + hci_skb_pkt_type(skb) = pkt_type; + hci_recv_frame(vbt->hdev, skb); } static void virtbt_rx_work(struct work_struct *work)