[PATCH 0/4] Use-after-free be gone

[Lukas Wunner <lukas@xxxxxxxxx>]

Here's my proposal to fix the use-after-free bugs reported by
Sascha Hauer and Florian Fainelli:

I scrutinized all SPI drivers in the v5.10 tree:

* There are 9 drivers with a use-after-free in the ->remove() hook
  caused by accessing driver private data after spi_unregister_controller().

* There are 8 drivers which leak the spi_controller in the ->probe()
  error path because of a missing spi_controller_put().

I'm introducing devm_spi_alloc_master/slave() which automatically
calls spi_controller_put() on ->remove().  This fixes both classes
of bugs while at the same time reducing code amount and complexity
in the ->probe() hook.

I propose that spi_controller_unregister() should no longer release
a reference on the spi_controller.  Instead, drivers need to either
do it themselves or use one of the devm functions introduced herein.
The vast majority of drivers can be converted to the devm functions.
See the commit message of patch [1/4] for the rationale and details.

Enclosed are patches for 3 Broadcom drivers.
Patches for the other drivers are on this branch:
https://github.com/l1k/linux/commits/spi_fixes

@Florian Fainelli:  Could you verify that there are no KASAN splats or
leaks with these patches?  Unfortunately I do not have any SPI-capable
hardware at my disposal right now, so can only compile-test.  You may
want to augment spi_controller_release() with a printk() to log when
the spi_controller is freed.

@Mark Brown:  Patches [2/4] to [4/4] reference the SHA-1 of patch [1/4]
in their stable tags.  Because the hash is unknown to me until you apply
the patch, I've used "123456789abc" as a placeholder.  You'll have to
replace the hash if/when applying.  Alternatively, only apply patch [1/4]
and I'll repost the other patches with the hash fixed up.

Thanks!


Lukas Wunner (4):
  spi: Introduce device-managed SPI controller allocation
  spi: bcm2835: Fix use-after-free on unbind
  spi: bcm2835aux: Fix use-after-free on unbind
  spi: bcm-qspi: Fix use-after-free on unbind

 drivers/spi/spi-bcm-qspi.c   | 34 ++++++++-------------
 drivers/spi/spi-bcm2835.c    | 24 +++++----------
 drivers/spi/spi-bcm2835aux.c | 21 +++++--------
 drivers/spi/spi.c            | 58 +++++++++++++++++++++++++++++++++++-
 include/linux/spi/spi.h      | 19 ++++++++++++
 5 files changed, 103 insertions(+), 53 deletions(-)

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2.28.0