Commit ab3428cf authored by Russell King (Oracle)'s avatar Russell King (Oracle) Committed by Greg Kroah-Hartman
Browse files

nvmem: core: fix registration vs use race 



The i.MX6 CPU frequency driver sometimes fails to register at boot time
due to nvmem_cell_read_u32() sporadically returning -ENOENT.

This happens because there is a window where __nvmem_device_get() in
of_nvmem_cell_get() is able to return the nvmem device, but as cells
have been setup, nvmem_find_cell_entry_by_node() returns NULL.

The occurs because the nvmem core registration code violates one of the
fundamental principles of kernel programming: do not publish data
structures before their setup is complete.

Fix this by making nvmem core code conform with this principle.

Fixes: eace75cf ("nvmem: Add a simple NVMEM framework for nvmem providers")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: default avatarSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20230127104015.23839-7-srinivas.kandagatla@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 560181d3

drivers/nvmem/core.c

+8 −10
Original line number Diff line number Diff line
@@ -832,22 +832,16 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) 
	nvmem->dev.groups = nvmem_dev_groups;

#endif



	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);



	rval = device_add(&nvmem->dev);

	if (rval)

		goto err_put_device;



	if (nvmem->nkeepout) {

		rval = nvmem_validate_keepouts(nvmem);

		if (rval)

			goto err_device_del;

			goto err_put_device;

	}



	if (config->compat) {

		rval = nvmem_sysfs_setup_compat(nvmem, config);

		if (rval)

			goto err_device_del;

			goto err_put_device;

	}



	if (config->cells) {
@@ -864,6 +858,12 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) 
	if (rval)

		goto err_remove_cells;



	dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", config->name);



	rval = device_add(&nvmem->dev);

	if (rval)

		goto err_remove_cells;



	blocking_notifier_call_chain(&nvmem_notifier, NVMEM_ADD, nvmem);



	return nvmem;
@@ -873,8 +873,6 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) 
err_teardown_compat:

	if (config->compat)

		nvmem_sysfs_remove_compat(nvmem, config);

err_device_del:

	device_del(&nvmem->dev);

err_put_device:

	put_device(&nvmem->dev);