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Bluetooth: MGMT: reject HCI_CMD_SYNC params_len above 255

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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 03f1700b9b ("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: 827af4787e ("Bluetooth: MGMT: Add initial implementation of MGMT_OP_HCI_CMD_SYNC")
Cc: stable@vger.kernel.org
Signed-off-by: Ali Ahmet Memis <ali@iusegentoo.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Ali Ahmet Memis
2026-08-06 17:39:53 +00:00
committed by Luiz Augusto von Dentz
parent e48e332d84
commit 5d95286b6d
1 changed files with 8 additions and 0 deletions
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8
net/bluetooth/mgmt.c
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@@ -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)