From: Shivam Kalra via B4 Relay <devnull+shivamkalra98.zohomail.in@kernel.org>
To: Marcel Holtmann <marcel@holtmann.org>,
Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Tristan Madani <tristan@talencesecurity.com>
Cc: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>,
linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mediatek@lists.infradead.org, stable@vger.kernel.org,
Shivam Kalra <shivamkalra98@zohomail.in>
Subject: [PATCH] Bluetooth: btmtk: Fix FUNC_CTRL parsing for devices with zero-length payloads
Date: Thu, 14 May 2026 23:18:13 +0530 [thread overview]
Message-ID: <20260514-bluetooh-fix-mt7922-v1-1-499c878af1e5@zohomail.in> (raw)
From: Shivam Kalra <shivamkalra98@zohomail.in>
Commit 634a4408c061 ("Bluetooth: btmtk: validate WMT event SKB length
before struct access") added strict SKB length checks to prevent OOB
memory reads when parsing WMT events.
However, when enabling the protocol (flag = 0), the MT7922 returns a WMT
event with a zero-length payload (skb->len == 7), omitting the 2-byte
status field entirely.
The strict sizeof() check unconditionally enforced the presence of the
status field for all BTMTK_WMT_FUNC_CTRL events. This caused the driver
to reject these payload-less responses with -EINVAL, failing Bluetooth
initialization ("Failed to send wmt func ctrl (-22)").
Fix this by making skb_pull_data() conditional: if the status payload is
present, parse it as before; if omitted, default to BTMTK_WMT_ON_UNDONE.
This restores the pre-regression initialization behavior while
maintaining the memory safety bounds of the previous patch.
Fixes: 634a4408c061 ("Bluetooth: btmtk: validate WMT event SKB length before struct access")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221511
Cc: stable@vger.kernel.org
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
---
Tested on a laptop with a single MediaTek MT7922 (USB ID 0489:e0e0)
Bluetooth controller. Before this patch, Bluetooth initialization failed
with "Failed to send wmt func ctrl (-22)" on every boot. After applying
this patch, initialization succeeds reliably.
This regression is also reported by other users on the kernel bug
tracker [1].
Note: btmtksdio.c and btmtkuart.c have similar FUNC_CTRL parsing code
but were not modified by the original commit 634a4408c061, so they are
not affected by this regression and do not require changes.
[1] https://bugzilla.kernel.org/show_bug.cgi?id=221511
---
drivers/bluetooth/btmtk.c | 24 ++++++++++++------------
1 file changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/bluetooth/btmtk.c b/drivers/bluetooth/btmtk.c
index f70c1b0f8990..026e5a76b086 100644
--- a/drivers/bluetooth/btmtk.c
+++ b/drivers/bluetooth/btmtk.c
@@ -717,19 +717,19 @@ static int btmtk_usb_hci_wmt_sync(struct hci_dev *hdev,
status = BTMTK_WMT_PATCH_DONE;
break;
case BTMTK_WMT_FUNC_CTRL:
- if (!skb_pull_data(data->evt_skb,
- sizeof(wmt_evt_funcc->status))) {
- err = -EINVAL;
- goto err_free_skb;
- }
-
- wmt_evt_funcc = (struct btmtk_hci_wmt_evt_funcc *)wmt_evt;
- if (be16_to_cpu(wmt_evt_funcc->status) == 0x404)
- status = BTMTK_WMT_ON_DONE;
- else if (be16_to_cpu(wmt_evt_funcc->status) == 0x420)
- status = BTMTK_WMT_ON_PROGRESS;
- else
+ if (skb_pull_data(data->evt_skb,
+ sizeof(wmt_evt_funcc->status))) {
+ wmt_evt_funcc =
+ (struct btmtk_hci_wmt_evt_funcc *)wmt_evt;
+ if (be16_to_cpu(wmt_evt_funcc->status) == 0x404)
+ status = BTMTK_WMT_ON_DONE;
+ else if (be16_to_cpu(wmt_evt_funcc->status) == 0x420)
+ status = BTMTK_WMT_ON_PROGRESS;
+ else
+ status = BTMTK_WMT_ON_UNDONE;
+ } else {
status = BTMTK_WMT_ON_UNDONE;
+ }
break;
case BTMTK_WMT_PATCH_DWNLD:
if (wmt_evt->whdr.flag == 2)
---
base-commit: 5d6919055dec134de3c40167a490f33c74c12581
change-id: 20260514-bluetooh-fix-mt7922-92bbbeff229b
Best regards,
--
Shivam Kalra <shivamkalra98@zohomail.in>
next reply other threads:[~2026-05-14 17:48 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-14 17:48 Shivam Kalra via B4 Relay [this message]
2026-05-16 19:15 ` [PATCH] Bluetooth: btmtk: Fix FUNC_CTRL parsing for devices with zero-length payloads Tristan Madani
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