Unverified Commit abd42781 authored Jun 18, 2020 by Zhenzhong Duan Committed by Mark Brown Jun 18, 2020

spi: spidev: fix a race between spidev_release and spidev_remove



Imagine below scene, spidev is referenced after it's freed.

spidev_release()                spidev_remove()
...
                                spin_lock_irq(&spidev->spi_lock);
                                    spidev->spi = NULL;
                                spin_unlock_irq(&spidev->spi_lock);
mutex_lock(&device_list_lock);
dofree = (spidev->spi == NULL);
if (dofree)
    kfree(spidev);
mutex_unlock(&device_list_lock);
                                mutex_lock(&device_list_lock);
                                list_del(&spidev->device_entry);
                                device_destroy(spidev_class, spidev->devt);
                                clear_bit(MINOR(spidev->devt), minors);
                                if (spidev->users == 0)
                                    kfree(spidev);
                                mutex_unlock(&device_list_lock);

Fix it by resetting spidev->spi in device_list_lock's protection.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com>
Link: https://lore.kernel.org/r/20200618032125.4650-1-zhenzhong.duan@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>

parent 35700e22

drivers/spi/spidev.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -787,13 +787,13 @@ static int spidev_remove(struct spi_device *spi)
		{
		struct spidev_data *spidev = spi_get_drvdata(spi);

		/* prevent new opens */
		mutex_lock(&device_list_lock);
		/* make sure ops on existing fds can abort cleanly */
		spin_lock_irq(&spidev->spi_lock);
		spidev->spi = NULL;
		spin_unlock_irq(&spidev->spi_lock);

		/* prevent new opens */
		mutex_lock(&device_list_lock);
		list_del(&spidev->device_entry);
		device_destroy(spidev_class, spidev->devt);
		clear_bit(MINOR(spidev->devt), minors);

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