[PATCH v6 0/2] gpiolib: don't allow user-space to crash the kernel with hot-unplugs

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

This is (hopefully) the final iteration of the changes that aim at fixing
the situation in which the user-space can provoke a NULL-pointer derefence
in the kernel when a GPIO device that's in use by user-space is removed.

v5 -> v6:
- signal an error in poll callbacks instead of returning 0 which would make
  the user-space assume a timeout occurred (which could lead to user-space
  spinning a timeout loop forever)

v4 -> v5:
- try to acquire the semaphore for reading and bail out of syscall callbacks
  immediately in case of lock contention

v3 -> v4:
- use function typedefs to make code cleaner
- add a blank line after down_write()

v2 -> v3:
- drop the helper variable in patch 1/2 as we won't be using it in 2/2
- refactor patch 2/2 to use locking wrappers around the syscall callbacks

v1 -> v2:
- add missing gdev->chip checks in patch 1/2
- add a second patch that protects the structures that can be accessed
  by user-space calls against concurrent removal

Bartosz Golaszewski (2):
  gpiolib: cdev: fix NULL-pointer dereferences
  gpiolib: protect the GPIO device against being dropped while in use by
    user-space

 drivers/gpio/gpiolib-cdev.c | 193 ++++++++++++++++++++++++++++++++----
 drivers/gpio/gpiolib.c      |   4 +
 drivers/gpio/gpiolib.h      |   5 +
 3 files changed, 180 insertions(+), 22 deletions(-)

-- 
2.37.2