[PATCH] spi: lpspi: Avoid potential use-after-free in probe()

["A. Sverdlin" <alexander.sverdlin@siemens.com>]

From: Alexander Sverdlin <alexander.sverdlin@siemens.com>

fsl_lpspi_probe() is allocating/disposing memory manually with
spi_alloc_host()/spi_alloc_target(), but uses
devm_spi_register_controller(). In case of error after the latter call the
memory will be explicitly freed in the probe function by
spi_controller_put() call, but used afterwards by "devm" management outside
probe() (spi_unregister_controller() <- devm_spi_unregister() below).

Unable to handle kernel NULL pointer dereference at virtual address 0000000000000070
...
Call trace:
 kernfs_find_ns
 kernfs_find_and_get_ns
 sysfs_remove_group
 sysfs_remove_groups
 device_remove_attrs
 device_del
 spi_unregister_controller
 devm_spi_unregister
 release_nodes
 devres_release_all
 really_probe
 driver_probe_device
 __device_attach_driver
 bus_for_each_drv
 __device_attach
 device_initial_probe
 bus_probe_device
 deferred_probe_work_func
 process_one_work
 worker_thread
 kthread
 ret_from_fork

Fixes: 5314987de5e5 ("spi: imx: add lpspi bus driver")
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@siemens.com>
---
 drivers/spi/spi-fsl-lpspi.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 11991eb126364..079035db7dd85 100644
--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -830,11 +830,11 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
 
 	is_target = of_property_read_bool((&pdev->dev)->of_node, "spi-slave");
 	if (is_target)
-		controller = spi_alloc_target(&pdev->dev,
-					      sizeof(struct fsl_lpspi_data));
+		controller = devm_spi_alloc_target(&pdev->dev,
+						   sizeof(struct fsl_lpspi_data));
 	else
-		controller = spi_alloc_host(&pdev->dev,
-					    sizeof(struct fsl_lpspi_data));
+		controller = devm_spi_alloc_host(&pdev->dev,
+						 sizeof(struct fsl_lpspi_data));
 
 	if (!controller)
 		return -ENOMEM;
-- 
2.44.0