[PATCH 0/2] Bluetooth: btmtksdio: Fix SKB handling in the TX path

[Chris Lu <chris.lu@mediatek.com>]

btmtksdio_tx_packet() rounds the SDIO transfer size up to the 256 byte
block size, but never grows the SKB accordingly, so the host controller
reads up to 255 bytes of uninitialised memory and sends it to the device,
and can read past the end of the buffer as well.

Patch 2 fixes that by padding the SKB with zeros. The padding is written
behind skb->tail, which is only safe once the driver owns the data
buffer, so patch 1 replaces the open-coded headroom check with
skb_cow_head() first. Patch 1 on its own changes no observable
behaviour, but it is a hard prerequisite, so both patches carry the same
Fixes: tag.

Both patches were previously part of a larger MT7928 series [1]. They
are unrelated to MT7928 and to the USB driver, so they are sent
separately here. The remaining parts of that series will follow as
separate topic branches.

Tested on a Chromebook with MT7921S: Bluetooth power on, then A2DP
connect and stream continuously for one hour without failure. The padding
added by patch 2 covers every packet whose length is not a multiple of
the block size, and the reallocation added by patch 1 covers every HCI
command, which hci_send_cmd_sync() always clones into hdev->sent_cmd.

[1] https://lore.kernel.org/linux-bluetooth/20260717072133.2858136-1-chris.lu@mediatek.com/

Chris Lu (2):
  Bluetooth: btmtksdio: Take exclusive ownership of the SKB before TX
  Bluetooth: btmtksdio: Fix out-of-bounds DMA read in the TX path

 drivers/bluetooth/btmtksdio.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

-- 
2.45.2