CVE-2026-90090

In the Linux kernel, the following vulnerability has been resolved:

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.