The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From ddf75be47ca748f8b12d28ac64d624354fddf189 Mon Sep 17 00:00:00 2001
From: Lukas Wunner lukas@wunner.de Date: Mon, 3 Aug 2020 13:09:01 +0200 Subject: [PATCH] spi: Prevent adding devices below an unregistering controller
CONFIG_OF_DYNAMIC and CONFIG_ACPI allow adding SPI devices at runtime using a DeviceTree overlay or DSDT patch. CONFIG_SPI_SLAVE allows the same via sysfs.
But there are no precautions to prevent adding a device below a controller that's being removed. Such a device is unusable and may not even be able to unbind cleanly as it becomes inaccessible once the controller has been torn down. E.g. it is then impossible to quiesce the device's interrupt.
of_spi_notify() and acpi_spi_notify() do hold a ref on the controller, but otherwise run lockless against spi_unregister_controller().
Fix by holding the spi_add_lock in spi_unregister_controller() and bailing out of spi_add_device() if the controller has been unregistered concurrently.
Fixes: ce79d54ae447 ("spi/of: Add OF notifier handler") Signed-off-by: Lukas Wunner lukas@wunner.de Cc: stable@vger.kernel.org # v3.19+ Cc: Geert Uytterhoeven geert+renesas@glider.be Cc: Octavian Purdila octavian.purdila@intel.com Cc: Pantelis Antoniou pantelis.antoniou@konsulko.com Link: https://lore.kernel.org/r/a8c3205088a969dc8410eec1eba9aface60f36af.159645103... Signed-off-by: Mark Brown broonie@kernel.org
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index c3008e423f59..c6ea760ea5f0 100644 --- a/drivers/spi/Kconfig +++ b/drivers/spi/Kconfig @@ -1017,4 +1017,7 @@ config SPI_SLAVE_SYSTEM_CONTROL
endif # SPI_SLAVE
+config SPI_DYNAMIC + def_bool ACPI || OF_DYNAMIC || SPI_SLAVE + endif # SPI diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 0b260484b4f5..92b8fb416dca 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -475,6 +475,12 @@ static LIST_HEAD(spi_controller_list); */ static DEFINE_MUTEX(board_lock);
+/* + * Prevents addition of devices with same chip select and + * addition of devices below an unregistering controller. + */ +static DEFINE_MUTEX(spi_add_lock); + /** * spi_alloc_device - Allocate a new SPI device * @ctlr: Controller to which device is connected @@ -554,7 +560,6 @@ static int spi_dev_check(struct device *dev, void *data) */ int spi_add_device(struct spi_device *spi) { - static DEFINE_MUTEX(spi_add_lock); struct spi_controller *ctlr = spi->controller; struct device *dev = ctlr->dev.parent; int status; @@ -582,6 +587,13 @@ int spi_add_device(struct spi_device *spi) goto done; }
+ /* Controller may unregister concurrently */ + if (IS_ENABLED(CONFIG_SPI_DYNAMIC) && + !device_is_registered(&ctlr->dev)) { + status = -ENODEV; + goto done; + } + /* Descriptors take precedence */ if (ctlr->cs_gpiods) spi->cs_gpiod = ctlr->cs_gpiods[spi->chip_select]; @@ -2797,6 +2809,10 @@ void spi_unregister_controller(struct spi_controller *ctlr) struct spi_controller *found; int id = ctlr->bus_num;
+ /* Prevent addition of new devices, unregister existing ones */ + if (IS_ENABLED(CONFIG_SPI_DYNAMIC)) + mutex_lock(&spi_add_lock); + device_for_each_child(&ctlr->dev, NULL, __unregister);
/* First make sure that this controller was ever added */ @@ -2817,6 +2833,9 @@ void spi_unregister_controller(struct spi_controller *ctlr) if (found == ctlr) idr_remove(&spi_master_idr, id); mutex_unlock(&board_lock); + + if (IS_ENABLED(CONFIG_SPI_DYNAMIC)) + mutex_unlock(&spi_add_lock); } EXPORT_SYMBOL_GPL(spi_unregister_controller);