From 8524c3588fbb9d5c1b876e6f908c42926845650d Mon Sep 17 00:00:00 2001 From: Chris Lu Date: Thu, 22 Oct 2026 11:21:48 +0800 Subject: [PATCH] Bluetooth: btmtk: drop zero-length ISO packets from endpoint padding The ISO interrupt IN endpoint delivers a fixed-size transfer that holds one HCI ISO packet and zero-fills the remainder. That padding belongs to the transfer rather than to the stream, so it has to be dropped instead of reported to the host. btmtk_recv_isopkt() keeps parsing it: the zero bytes read as an ISO header with handle 0 and a Data_Total_Length of zero, and each one is passed to hci_recv_frame() as a complete frame. A single transfer yields a long run of them, which is what fills the HCI log with malformed ISO packets, and iso_recv() drops the SDU it is reassembling whenever handle 0 belongs to a live CIS/BIS. A zero Data_Total_Length carries no ISO Data Load, so such a packet is never part of the stream. Check for the zero-filled remainder before starting to parse the next frame, rather than after assembling a 4-byte header: a remainder shorter than HCI_ISO_HDR_SIZE would otherwise be held across calls as a partial header, corrupting the next transfer's framing. This also means a fully zero-filled remainder no longer costs an skb allocation that gets immediately freed. Reaching a zero Data_Total_Length any other way is then a genuine error, not padding. This was observed on MT7925, but btmtk_recv_isopkt() is shared by every MediaTek USB controller that supports ISO data. 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 | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c index 75483d8230e1..01d5ad2479f4 100644 --- a/drivers/bluetooth/btmtk.c +++ b/drivers/bluetooth/btmtk.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -1565,6 +1566,14 @@ static int btmtk_recv_isopkt(struct hci_dev *hdev, void *buffer, int count) int len; if (!skb) { + /* Drop the endpoint's zero-filled padding before + * allocating an skb for it; a zero Data_Total_Length + * check below would miss a padding remainder + * shorter than an ISO header. + */ + if (mem_is_zero(buffer, count)) + break; + skb = bt_skb_alloc(HCI_MAX_ISO_SIZE, GFP_ATOMIC); if (!skb) { err = -ENOMEM; @@ -1588,6 +1597,17 @@ static int btmtk_recv_isopkt(struct hci_dev *hdev, void *buffer, int count) /* Complete ISO header */ hci_skb_expect(skb) = __le16_to_cpu(dlen); + if (!hci_skb_expect(skb)) { + /* Zero padding was ruled out above, so a + * zero Data_Total_Length here is invalid. + */ + kfree_skb(skb); + skb = NULL; + + err = -EILSEQ; + break; + } + if (skb_tailroom(skb) < hci_skb_expect(skb)) { kfree_skb(skb); skb = NULL;