From 5d95286b6d6e8f1d304da7522bfa6860fc017e48 Mon Sep 17 00:00:00 2001 From: Ali Ahmet Memis Date: Thu, 6 Aug 2026 17:39:53 +0000 Subject: [PATCH] Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255 mgmt_hci_cmd_sync() checks that the message length agrees with params_len but puts no upper bound on it. params_len is __le16 while the parameter length in the HCI command header is a u8: struct hci_command_hdr { __le16 opcode; __u8 plen; } __packed; hci_cmd_sync_alloc() assigns one to the other: hdr->plen = plen; if (plen) skb_put_data(skb, param, plen); so a params_len of 256 leaves plen at 0 while all 256 bytes are still appended. The frame handed to the driver then declares no parameters and carries 256 of them. On a length framed transport such as H:4 the controller takes the trailing bytes as the start of the next packet. The mgmt socket MTU is HCI_MAX_FRAME_SIZE, so params_len can reach about 1KB this way. Commit 03f1700b9b4d ("Bluetooth: MGMT: reject malformed HCI_CMD_SYNC commands") only made params_len agree with the message length, a value that fits the message but not the header field is still accepted. Reject params_len that does not fit the header field. Fixes: 827af4787e74 ("Bluetooth: MGMT: Add initial implementation of MGMT_OP_HCI_CMD_SYNC") Cc: stable@vger.kernel.org Signed-off-by: Ali Ahmet Memis Signed-off-by: Luiz Augusto von Dentz --- net/bluetooth/mgmt.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c index c4ba845f7e5d..860c086011b7 100644 --- a/net/bluetooth/mgmt.c +++ b/net/bluetooth/mgmt.c @@ -2681,6 +2681,14 @@ static int mgmt_hci_cmd_sync(struct sock *sk, struct hci_dev *hdev, return mgmt_cmd_status(sk, hdev->id, MGMT_OP_HCI_CMD_SYNC, MGMT_STATUS_INVALID_PARAMS); + /* The HCI command header carries the parameter length in a u8, a + * larger value would be truncated there while the parameters are + * still appended to the frame in full. + */ + if (le16_to_cpu(cp->params_len) > U8_MAX) + return mgmt_cmd_status(sk, hdev->id, MGMT_OP_HCI_CMD_SYNC, + MGMT_STATUS_INVALID_PARAMS); + hci_dev_lock(hdev); cmd = mgmt_pending_new(sk, MGMT_OP_HCI_CMD_SYNC, hdev, data, len); if (!cmd)