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[ Upstream commitc56610a869] For ACPI drivers that provide a ->notify() callback and set ACPI_DRIVER_ALL_NOTIFY_EVENTS in their flags, that callback can be invoked while either the ->add() or the ->remove() callback is running without any synchronization at the bus type level which is counter to the common-sense expectation that notification handling should only be enabled when the driver is actually bound to the device. As a result, if the driver is not careful enough, it's ->notify() callback may crash when it is invoked too early or too late [1]. This issue has been amplified by commitd6fb6ee182("ACPI: bus: Drop driver member of struct acpi_device") that made acpi_bus_notify() check for the presence of the driver and its ->notify() callback directly instead of using an extra driver pointer that was only set and cleared by the bus type code, but it was present before that commit although it was harder to reproduce then. It can be addressed by using the observation that acpi_device_install_notify_handler() can be modified to install the handler for all types of events when ACPI_DRIVER_ALL_NOTIFY_EVENTS is set in the driver flags, in which case acpi_bus_notify() will not need to invoke the driver's ->notify() callback any more and that callback will only be invoked after acpi_device_install_notify_handler() has run and before acpi_device_remove_notify_handler() runs, which implies the correct ordering with respect to the other ACPI driver callbacks. Modify the code accordingly and while at it, drop two redundant local variables from acpi_bus_notify() and turn its description comment into a proper kerneldoc one. Fixes:d6fb6ee182("ACPI: bus: Drop driver member of struct acpi_device") Link: https://lore.kernel.org/linux-acpi/9f6cba7a8a57e5a687c934e8e406e28c.squirrel@mail.panix.com # [1] Reported-by: Pierre Asselin <pa@panix.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Pierre Asselin <pa@panix.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.