usb: host: max3421-hcd: Fix error pointer dereference in probe cleanup

[ Upstream commit 186e8f2bdba551f3ae23396caccd452d985c23e3 ]

The kthread_run() function returns error pointers so the
max3421_hcd->spi_thread pointer can be either error pointers or NULL.
Check for both before dereferencing it.

Fixes: 05dfa5c ("usb: host: max3421-hcd: fix "spi_rd8" uses dynamic stack allocation warning")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/aJTMVAPtRe5H6jug@stanley.mountain
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Ulrich Hecht <uli@kernel.org>

Author: Dan Carpenter

drivers/usb/host/max3421-hcd.c

@@ -1942,7 +1942,7 @@ max3421_probe(struct spi_device *spi)
 	if (hcd) {
 		kfree(max3421_hcd->tx);
 		kfree(max3421_hcd->rx);
-		if (max3421_hcd->spi_thread)
+		if (!IS_ERR_OR_NULL(max3421_hcd->spi_thread))
 			kthread_stop(max3421_hcd->spi_thread);
 		usb_put_hcd(hcd);
 	}