From fa0ad2d277c7adead61d1c22411c55cea6990c2a Mon Sep 17 00:00:00 2001 From: Chris Lu Date: Mon, 17 Aug 2026 17:53:32 +0800 Subject: [PATCH] Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path btmtksdio_tx_packet() rounds the transfer size up to the SDIO block size of 256 bytes, but hands the host controller the SKB buffer as is: err = sdio_writesb(bdev->func, MTK_REG_CTDR, skb->data, round_up(skb->len, MTK_SDIO_BLOCK_SIZE)); Only skb->len bytes hold packet data, so the controller reads up to 255 bytes of uninitialised memory and sends it to the device over the SDIO bus. Depending on how much tailroom slack the SKB allocation happens to carry, that read can also extend past the end of the buffer. Compute the padded length up front, ensure the SKB has tailroom for it, and zero-fill the padding with skb_put_zero(). skb->len then covers the padding, so sdio_writesb() no longer needs to round up. byte_tx keeps counting the header and the payload only, and the error path restores the SKB so that the caller can requeue it. Writing behind skb->tail is only safe because the driver owns the buffer, which "Bluetooth: btmtksdio: Take exclusive ownership of the SKB before TX" ensures. Fixes: 9aebfd4a2200 ("Bluetooth: mediatek: add support for MediaTek MT7663S and MT7668S SDIO devices") Signed-off-by: Chris Lu Assisted-by: Claude:claude-opus-5 Signed-off-by: Luiz Augusto von Dentz --- drivers/bluetooth/btmtksdio.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/drivers/bluetooth/btmtksdio.c b/drivers/bluetooth/btmtksdio.c index 8052e24d503b..94aa60d9cc20 100644 --- a/drivers/bluetooth/btmtksdio.c +++ b/drivers/bluetooth/btmtksdio.c @@ -272,6 +272,7 @@ static int btmtksdio_tx_packet(struct btmtksdio_dev *bdev, struct sk_buff *skb) { struct mtkbtsdio_hdr *sdio_hdr; + unsigned int len, pad_len; int err; /* Make sure that the data buffer is not shared with anyone else and @@ -281,6 +282,18 @@ static int btmtksdio_tx_packet(struct btmtksdio_dev *bdev, if (err < 0) return err; + /* The transfer is rounded up to the SDIO block size, so the buffer + * has to provide tailroom for the padding as well + */ + len = skb->len + sizeof(*sdio_hdr); + pad_len = round_up(len, MTK_SDIO_BLOCK_SIZE) - len; + + if (unlikely(skb_tailroom(skb) < pad_len)) { + err = pskb_expand_head(skb, 0, pad_len, GFP_ATOMIC); + if (err < 0) + return err; + } + /* Prepend MediaTek SDIO Specific Header */ skb_push(skb, sizeof(*sdio_hdr)); @@ -289,19 +302,22 @@ static int btmtksdio_tx_packet(struct btmtksdio_dev *bdev, sdio_hdr->reserved = cpu_to_le16(0); sdio_hdr->bt_type = hci_skb_pkt_type(skb); - clear_bit(BTMTKSDIO_HW_TX_READY, &bdev->tx_state); - err = sdio_writesb(bdev->func, MTK_REG_CTDR, skb->data, - round_up(skb->len, MTK_SDIO_BLOCK_SIZE)); - if (err < 0) - goto err_skb_pull; + /* Zero the padding so that no uninitialised memory is sent out */ + skb_put_zero(skb, pad_len); - bdev->hdev->stat.byte_tx += skb->len; + clear_bit(BTMTKSDIO_HW_TX_READY, &bdev->tx_state); + err = sdio_writesb(bdev->func, MTK_REG_CTDR, skb->data, skb->len); + if (err < 0) + goto err_skb_restore; + + bdev->hdev->stat.byte_tx += len; kfree_skb(skb); return 0; -err_skb_pull: +err_skb_restore: + skb_trim(skb, len); skb_pull(skb, sizeof(*sdio_hdr)); return err;