From 6c53b45c71b4920b5e62f0ea8079a1da382b9434 Mon Sep 17 00:00:00 2001 From: Michael Walle Date: Thu, 11 Nov 2021 09:37:13 +0100 Subject: [PATCH] spi: fix use-after-free of the add_lock mutex MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Commit 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses") introduced a per-controller mutex. But mutex_unlock() of said lock is called after the controller is already freed: spi_unregister_controller(ctlr) -> put_device(&ctlr->dev) -> spi_controller_release(dev) -> mutex_unlock(&ctrl->add_lock) Move the put_device() after the mutex_unlock(). Fixes: 6098475d4cb4 ("spi: Fix deadlock when adding SPI controllers on SPI buses") Signed-off-by: Michael Walle Reviewed-by: Uwe Kleine-König Reviewed-by: Lukas Wunner Cc: stable@vger.kernel.org # v5.15 Link: https://lore.kernel.org/r/20211111083713.3335171-1-michael@walle.cc Signed-off-by: Mark Brown --- drivers/spi/spi.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 72826bdab270..a2988aed984c 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -3058,12 +3058,6 @@ void spi_unregister_controller(struct spi_controller *ctlr) device_del(&ctlr->dev); - /* Release the last reference on the controller if its driver - * has not yet been converted to devm_spi_alloc_master/slave(). - */ - if (!ctlr->devm_allocated) - put_device(&ctlr->dev); - /* free bus id */ mutex_lock(&board_lock); if (found == ctlr) @@ -3072,6 +3066,12 @@ void spi_unregister_controller(struct spi_controller *ctlr) if (IS_ENABLED(CONFIG_SPI_DYNAMIC)) mutex_unlock(&ctlr->add_lock); + + /* Release the last reference on the controller if its driver + * has not yet been converted to devm_spi_alloc_master/slave(). + */ + if (!ctlr->devm_allocated) + put_device(&ctlr->dev); } EXPORT_SYMBOL_GPL(spi_unregister_controller); -- 2.20.1