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spi: spidev: fix a potential use-after-free in spidev_release()

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If an spi device is unbounded from the driver before the release
process, there will be an NULL pointer reference when it's
referenced in spi_slave_abort().

Fix it by checking it's already freed before reference.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com>
Link: https://lore.kernel.org/r/20200618032125.4650-2-zhenzhong.duan@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Zhenzhong Duan 2020-06-18 11:21:25 +08:00 committed by Mark Brown
parent abd42781c3
commit 06096cc6c5
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GPG Key ID: 24D68B725D5487D0
1 changed files with 10 additions and 10 deletions
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20
drivers/spi/spidev.c
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@ -609,15 +609,20 @@ static int spidev_open(struct inode *inode, struct file *filp)
static int spidev_release(struct inode *inode, struct file *filp)
{
struct spidev_data *spidev;
int dofree;
mutex_lock(&device_list_lock);
spidev = filp->private_data;
filp->private_data = NULL;
spin_lock_irq(&spidev->spi_lock);
/* ... after we unbound from the underlying device? */
dofree = (spidev->spi == NULL);
spin_unlock_irq(&spidev->spi_lock);
/* last close? */
spidev->users--;
if (!spidev->users) {
int dofree;
kfree(spidev->tx_buffer);
spidev->tx_buffer = NULL;
@ -625,19 +630,14 @@ static int spidev_release(struct inode *inode, struct file *filp)
kfree(spidev->rx_buffer);
spidev->rx_buffer = NULL;
spin_lock_irq(&spidev->spi_lock);
if (spidev->spi)
spidev->speed_hz = spidev->spi->max_speed_hz;
/* ... after we unbound from the underlying device? */
dofree = (spidev->spi == NULL);
spin_unlock_irq(&spidev->spi_lock);
if (dofree)
kfree(spidev);
else
spidev->speed_hz = spidev->spi->max_speed_hz;
}
#ifdef CONFIG_SPI_SLAVE
spi_slave_abort(spidev->spi);
if (!dofree)
spi_slave_abort(spidev->spi);
#endif
mutex_unlock(&device_list_lock);