[PATCH 4.2 085/258] spi: spidev: fix possible NULL dereference

[Greg Kroah-Hartman]

4.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>

commit dd85ebf681ef0ee1fc985c353dd45e8b53b5dc1e upstream.

During the last close we are freeing spidev if spidev->spi is NULL, but
just before checking if spidev->spi is NULL we are dereferencing it.
Lets add a check there to avoid the NULL dereference.

Fixes: 9169051617df ("spi: spidev: Don't mangle max_speed_hz in underlying spi device")
Signed-off-by: Sudip Mukherjee <sudip@xxxxxxxxxxxxxxx>
Reviewed-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Tested-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/spi/spidev.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -651,7 +651,8 @@ static int spidev_release(struct inode *
 		kfree(spidev->rx_buffer);
 		spidev->rx_buffer = NULL;
 
-		spidev->speed_hz = spidev->spi->max_speed_hz;
+		if (spidev->spi)
+			spidev->speed_hz = spidev->spi->max_speed_hz;
 
 		/* ... after we unbound from the underlying device? */
 		spin_lock_irq(&spidev->spi_lock);


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