[PATCH v4 0/3] Input/SPI: fixes for MacBook8,1 DMA timeout, UAF, and NULL pointer dereference

[Shih-Yuan Lee <fourdollars@debian.org>]

Hi Dmitry, Mark, and the linux-input/linux-spi community,

This patch series addresses a long-standing DMA initialization timeout on the 
early 2015 12" MacBook (MacBook8,1) on any boot (including cold boot), as well 
as two pre-existing, high-severity UAF/NULL-pointer bugs in the applespi driver.

Changes in v4:
  - Reverted the runtime `can_dma` callback override from `applespi.c` to avoid 
    architectural layering violation, data races (TOCTOU) with concurrent SPI 
    transfers, and execute-after-free vulnerability upon module unload.
  - Moved the DMI quirk forcing PIO mode for MacBook8,1 to the host PCI glue 
    driver (spi-pxa2xx-pci.c) where LPSS setup occurs.
  - Formatted the DMI match using a structured `pxa2xx_spi_pci_dmi_table` and 
    helper function `pxa2xx_spi_pci_can_dma()`.
  - Added a `force_pio` module parameter in spi-pxa2xx-pci.c to allow other 
    users to manually force PIO mode for debugging.

Changes in v3:
  - Added a `force_pio` module parameter to applespi to allow users to manually 
    disable DMA for SPI transfers.
  - Resolved the execute-after-free vulnerability by unconditionally restoring 
    the original can_dma callback (even if NULL) in the driver remove path.
  - Fixed the probe timing issue by applying the can_dma override at the very 
    beginning of applespi_probe() so that all early initialization transfers 
    safely use PIO mode, and properly restoring it in all probe error paths.
  - Documented the Bugzilla link in the commit message of Patch 1.

Changes in v2:
  - Fixed an unbind/remove execute-after-free vulnerability by storing and 
    restoring the host controller's original can_dma callback in applespi_probe() 
    and applespi_remove().
  - Split the fixes into a 3-patch logical series.

Patch 1 fixes a pre-existing UAF vulnerability in the driver unbind path by 
explicitly calling cancel_work_sync() on the asynchronous registration worker 
work struct before devres frees the driver private data.

Patch 2 fixes a pre-existing race condition in the debugfs interface where 
userspace could open the tp_dim file before the asynchronous worker has 
finished initializing applespi->touchpad_input_dev, leading to a NULL 
pointer dereference. We resolve this using smp_load_acquire() and checking 
for NULL.

Patch 3 introduces a structured DMI quirk and a `force_pio` module parameter 
in spi-pxa2xx-pci.c to disable DMA on MacBook8,1. This forces the controller 
to use the rock-solid PIO mode from the very beginning.

Best regards,
Shih-Yuan Lee

Shih-Yuan Lee (3):
  Input: applespi - cancel pending work on driver remove
  Input: applespi - fix NULL pointer dereference in tp_dim open
  spi: pxa2xx: disable DMA for Apple MacBook8,1

 drivers/input/keyboard/applespi.c | 10 +++++++++-
 drivers/spi/spi-pxa2xx-pci.c      | 33 ++++++++++++++++++++++++++++++-
 2 files changed, 41 insertions(+), 2 deletions(-)

-- 
2.39.5