From: Bartosz Golaszewski bartosz.golaszewski@linaro.org
[ Upstream commit a720416d94634068951773cb9e9d6f1b73769e5b ]
There's a spinlock in place that is taken in file_operations callbacks whenever we check if spidev->spi is still alive (not null). It's also taken when spidev->spi is set to NULL in remove().
This however doesn't protect the code against driver unbind event while one of the syscalls is still in progress. To that end we need a lock taken continuously as long as we may still access spidev->spi. As both the file ops and the remove callback are never called from interrupt context, we can replace the spinlock with a mutex.
Signed-off-by: Bartosz Golaszewski bartosz.golaszewski@linaro.org Link: https://lore.kernel.org/r/20230106100719.196243-1-brgl@bgdev.pl Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/spi/spidev.c | 34 ++++++++++++++++++---------------- 1 file changed, 18 insertions(+), 16 deletions(-)
diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c index 6313e7d0cdf8..42aaaca67265 100644 --- a/drivers/spi/spidev.c +++ b/drivers/spi/spidev.c @@ -68,7 +68,7 @@ static_assert(N_SPI_MINORS > 0 && N_SPI_MINORS <= 256);
struct spidev_data { dev_t devt; - spinlock_t spi_lock; + struct mutex spi_lock; struct spi_device *spi; struct list_head device_entry;
@@ -95,9 +95,8 @@ spidev_sync(struct spidev_data *spidev, struct spi_message *message) int status; struct spi_device *spi;
- spin_lock_irq(&spidev->spi_lock); + mutex_lock(&spidev->spi_lock); spi = spidev->spi; - spin_unlock_irq(&spidev->spi_lock);
if (spi == NULL) status = -ESHUTDOWN; @@ -107,6 +106,7 @@ spidev_sync(struct spidev_data *spidev, struct spi_message *message) if (status == 0) status = message->actual_length;
+ mutex_unlock(&spidev->spi_lock); return status; }
@@ -359,12 +359,12 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) * we issue this ioctl. */ spidev = filp->private_data; - spin_lock_irq(&spidev->spi_lock); + mutex_lock(&spidev->spi_lock); spi = spi_dev_get(spidev->spi); - spin_unlock_irq(&spidev->spi_lock); - - if (spi == NULL) + if (spi == NULL) { + mutex_unlock(&spidev->spi_lock); return -ESHUTDOWN; + }
/* use the buffer lock here for triple duty: * - prevent I/O (from us) so calling spi_setup() is safe; @@ -508,6 +508,7 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
mutex_unlock(&spidev->buf_lock); spi_dev_put(spi); + mutex_unlock(&spidev->spi_lock); return retval; }
@@ -529,12 +530,12 @@ spidev_compat_ioc_message(struct file *filp, unsigned int cmd, * we issue this ioctl. */ spidev = filp->private_data; - spin_lock_irq(&spidev->spi_lock); + mutex_lock(&spidev->spi_lock); spi = spi_dev_get(spidev->spi); - spin_unlock_irq(&spidev->spi_lock); - - if (spi == NULL) + if (spi == NULL) { + mutex_unlock(&spidev->spi_lock); return -ESHUTDOWN; + }
/* SPI_IOC_MESSAGE needs the buffer locked "normally" */ mutex_lock(&spidev->buf_lock); @@ -561,6 +562,7 @@ spidev_compat_ioc_message(struct file *filp, unsigned int cmd, done: mutex_unlock(&spidev->buf_lock); spi_dev_put(spi); + mutex_unlock(&spidev->spi_lock); return retval; }
@@ -640,10 +642,10 @@ static int spidev_release(struct inode *inode, struct file *filp) spidev = filp->private_data; filp->private_data = NULL;
- spin_lock_irq(&spidev->spi_lock); + mutex_lock(&spidev->spi_lock); /* ... after we unbound from the underlying device? */ dofree = (spidev->spi == NULL); - spin_unlock_irq(&spidev->spi_lock); + mutex_unlock(&spidev->spi_lock);
/* last close? */ spidev->users--; @@ -776,7 +778,7 @@ static int spidev_probe(struct spi_device *spi)
/* Initialize the driver data */ spidev->spi = spi; - spin_lock_init(&spidev->spi_lock); + mutex_init(&spidev->spi_lock); mutex_init(&spidev->buf_lock);
INIT_LIST_HEAD(&spidev->device_entry); @@ -821,9 +823,9 @@ static void spidev_remove(struct spi_device *spi) /* prevent new opens */ mutex_lock(&device_list_lock); /* make sure ops on existing fds can abort cleanly */ - spin_lock_irq(&spidev->spi_lock); + mutex_lock(&spidev->spi_lock); spidev->spi = NULL; - spin_unlock_irq(&spidev->spi_lock); + mutex_unlock(&spidev->spi_lock);
list_del(&spidev->device_entry); device_destroy(spidev_class, spidev->devt);