From d015faf684129a276f2137ad2e11c6c985294648 Mon Sep 17 00:00:00 2001 From: Chris Lu Date: Thu, 22 Oct 2026 11:21:49 +0800 Subject: [PATCH] Bluetooth: btmtk: bound the ISO payload length by the controller's MTU btmtk_recv_isopkt() bounds the Data_Total_Length reported by the controller with skb_tailroom(skb) < hci_skb_expect(skb). That keeps the reassembly inside the skb, but it enforces no protocol limit: the head allocation is rounded up to the next kmalloc bucket and skb_tailroom() reports what the bucket can hold rather than what was requested, which is several hundred bytes more. An oversized length therefore passes, and the parser keeps pulling bytes out of the following transfers to fill it, swallowing the real ISO packets they carry until the frame is handed to hci_recv_frame(). The controller reports the largest ISO_Data_Packet_Length it will send in LE Read Buffer Size [v2], which hci_cc_le_read_buffer_size_v2() keeps in hdev->iso_mtu. Once that is available, bound the length by it and size the receive skb to hold that much plus the 4-byte header. HCI_MAX_ISO_SIZE is kept only as a fallback for the window before the command completes. Keep the skb_tailroom() test as well, because a fragment started before hdev->iso_mtu was populated sits in an skb sized for the fallback. Fixes: ceac1cb0259d ("Bluetooth: btusb: mediatek: add ISO data transmission functions") Co-developed-by: Hao Qin Signed-off-by: Hao Qin Co-developed-by: Wenlong Tian Signed-off-by: Wenlong Tian Signed-off-by: Chris Lu Signed-off-by: Luiz Augusto von Dentz --- drivers/bluetooth/btmtk.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c index 01d5ad2479f4..f2224eb0bf6b 100644 --- a/drivers/bluetooth/btmtk.c +++ b/drivers/bluetooth/btmtk.c @@ -1557,8 +1557,15 @@ static int btmtk_recv_isopkt(struct hci_dev *hdev, void *buffer, int count) struct btmtk_data *btmtk_data = hci_get_priv(hdev); struct sk_buff *skb; unsigned long flags; + unsigned int iso_mtu; int err = 0; + /* The controller reports the largest Data_Total_Length it will send in + * LE Read Buffer Size [v2]. Fall back to HCI_MAX_ISO_SIZE while that + * command has not completed yet. + */ + iso_mtu = hdev->iso_mtu ? hdev->iso_mtu : HCI_MAX_ISO_SIZE; + spin_lock_irqsave(&btmtk_data->isorxlock, flags); skb = btmtk_data->isopkt_skb; @@ -1574,7 +1581,8 @@ static int btmtk_recv_isopkt(struct hci_dev *hdev, void *buffer, int count) if (mem_is_zero(buffer, count)) break; - skb = bt_skb_alloc(HCI_MAX_ISO_SIZE, GFP_ATOMIC); + skb = bt_skb_alloc(HCI_ISO_HDR_SIZE + iso_mtu, + GFP_ATOMIC); if (!skb) { err = -ENOMEM; break; @@ -1608,7 +1616,13 @@ static int btmtk_recv_isopkt(struct hci_dev *hdev, void *buffer, int count) break; } - if (skb_tailroom(skb) < hci_skb_expect(skb)) { + /* Reject a length the controller said it would never + * send. The skb_tailroom() test is kept because a + * fragment started before hdev->iso_mtu was populated + * sits in a smaller skb than iso_mtu now allows. + */ + if (hci_skb_expect(skb) > iso_mtu || + skb_tailroom(skb) < hci_skb_expect(skb)) { kfree_skb(skb); skb = NULL;