[PATCH v3 1/2] leds: tca6507: Fix use-after-free on unbind

[Danish Khateeb]

Since the LEDs are registered with devm_led_classdev_register(), they
are unregistered only after tca6507_remove() has cancelled the work.
Unregistering an LED that is on turns it off, which queues the work
again from led_assign(), and the work then runs after devres has freed
the chip:

  BUG: KASAN: slab-use-after-free in assign_work+0x414/0x5b0
  Read of size 8 at addr ffff888010d5c0c0 by task kworker/1:2/65
  ...
  Last potentially related work creation:
   ...
   queue_work_on+0xb6/0xc0
   led_assign+0x223/0x340 [leds_tca6507]
   led_classdev_unregister+0x26b/0x340
   release_nodes+0xb3/0x140
   devres_release_group+0x247/0x470
   i2c_device_remove+0xbf/0x1b0

Set up the work with devm_work_autocancel() before the LEDs are
registered, so that devres cancels it after they are gone, and drop
tca6507_remove().

Fixes: 1b5c2fa7081c ("leds: tca6507: Use devm_led_classdev_register() to simplify remove path")
Cc: stable@xxxxxxxxxxxxxxx
Acked-by: Andrew Davis <afd@xxxxxx>
Signed-off-by: Danish Khateeb <danishkhateeb03@xxxxxxxxx>
---
 drivers/leds/leds-tca6507.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-tca6507.c b/drivers/leds/leds-tca6507.c
index 9afe2722986c..0f987e551f03 100644
--- a/drivers/leds/leds-tca6507.c
+++ b/drivers/leds/leds-tca6507.c
@@ -71,6 +71,7 @@
  * not recognised when matching.
  */
 
+#include <linux/devm-helpers.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/leds.h>
@@ -735,9 +736,11 @@ static int tca6507_probe(struct i2c_client *client)
 		return -ENOMEM;
 
 	tca->client = client;
-	INIT_WORK(&tca->work, tca6507_work);
 	spin_lock_init(&tca->lock);
-	i2c_set_clientdata(client, tca);
+
+	err = devm_work_autocancel(dev, &tca->work, tca6507_work);
+	if (err)
+		return err;
 
 	for (i = 0; i < NUM_LEDS; i++) {
 		struct tca6507_led *l = tca->leds + i;
@@ -766,20 +769,12 @@ static int tca6507_probe(struct i2c_client *client)
 	return 0;
 }
 
-static void tca6507_remove(struct i2c_client *client)
-{
-	struct tca6507_chip *tca = i2c_get_clientdata(client);
-
-	cancel_work_sync(&tca->work);
-}
-
 static struct i2c_driver tca6507_driver = {
 	.driver   = {
 		.name    = "leds-tca6507",
 		.of_match_table = of_match_ptr(of_tca6507_leds_match),
 	},
 	.probe    = tca6507_probe,
-	.remove   = tca6507_remove,
 	.id_table = tca6507_id,
 };
 
-- 
2.56.0