[PATCH] mfd: cros_ec: Delay dev_set_drvdata() until probe success

[Andrei Kuchynski]

If ec_device_probe() fails, cros_ec_class_release releases memory for the
cros_ec_dev structure. However, because the drvdata was already set,
sub-drivers like cros_ec_typec can still retrieve the stale pointer via the
platform device. This leads to a use-after-free when cros_ec_typec attempts
to access &typec->ec->ec->dev on a device that has already been released.
Move dev_set_drvdata() to ensure that the pointer is only made available
once all initialization steps have succeeded.

 sysfs: cannot create duplicate filename '/class/chromeos/cros_ec'
 Call trace:
  sysfs_do_create_link_sd+0x94/0xdc
  sysfs_create_link+0x30/0x44
  device_add_class_symlinks+0x90/0x13c
  device_add+0xf0/0x50c
  ec_device_probe+0x150/0x4f0
  platform_probe+0xa0/0xe0
 ...
 BUG: KASAN: invalid-access in __memcpy+0x44/0x230
 Write at addr f5ffff809e2d33ac by task kworker/u32:5/125
 Pointer tag: [f5], memory tag: [fe]
 Tainted : [W]=WARN, [O]=OOT_MODULE
 Hardware name: Google Navi unprovisioned 0x7FFFFFFF/sku0 board/sku3
 Workqueue: events_unbound deferred_probe_work_func
 Call trace:
  __memcpy+0x44/0x230
  cros_ec_check_features+0x60/0xcc [cros_ec_proto]
  cros_typec_probe+0xe8/0x6e0 [cros_ec_typec]
  platform_probe+0xa0/0xe0

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 1c1d152cc5ac ("platform/chrome: cros_ec_dev - utilize new cdev_device_add helper function")
Co-developed-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Signed-off-by: Andrei Kuchynski <akuchynski@xxxxxxxxxxxx>
---
 drivers/mfd/cros_ec_dev.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
index 39430dd44e30c..56fb7cceafc6c 100644
--- a/drivers/mfd/cros_ec_dev.c
+++ b/drivers/mfd/cros_ec_dev.c
@@ -195,7 +195,6 @@ static int ec_device_probe(struct platform_device *pdev)
 	if (!ec)
 		return retval;
 
-	dev_set_drvdata(dev, ec);
 	ec->ec_dev = dev_get_drvdata(dev->parent);
 	ec->dev = dev;
 	ec->cmd_offset = ec_platform->cmd_offset;
@@ -237,6 +236,8 @@ static int ec_device_probe(struct platform_device *pdev)
 	if (retval)
 		goto failed;
 
+	dev_set_drvdata(dev, ec);
+
 	/* check whether this EC is a sensor hub. */
 	if (cros_ec_get_sensor_count(ec) > 0) {
 		retval = mfd_add_hotplug_devices(ec->dev,
-- 
2.54.0.rc2.544.gc7ae2d5bb8-goog