linux-kernel - [PATCH v3 2/2] rpmsg: glink: Update cdev add/del API in rpmsg_ctrldev_release

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Message-Id: <20211102165137.v3.2.Ie09561c5b453a91f10ecc7e1974c602c4ff78245@changeid>
Date:   Tue,  2 Nov 2021 16:51:51 -0700
From:   Sujit Kautkar <sujitka@...omium.org>
To:     Andy Gross <agross@...nel.org>, Ohad Ben-Cohen <ohad@...ery.com>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Sujit Kautkar <sujitka@...omium.org>,
        linux-kernel@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: [PATCH v3 2/2] rpmsg: glink: Update cdev add/del API in rpmsg_ctrldev_release_device()

Replace cdev add/del APIs with cdev_device_add/cdev_device_del to avoid
below kernel warning. This correctly takes a reference to the parent
device so the parent will not get released until all references to the
cdev are released.

| ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x7c
| WARNING: CPU: 7 PID: 19892 at lib/debugobjects.c:488 debug_print_object+0x13c/0x1b0
| CPU: 7 PID: 19892 Comm: kworker/7:4 Tainted: G        W         5.4.147-lockdep #1
| ==================================================================
| Hardware name: Google CoachZ (rev1 - 2) with LTE (DT)
| Workqueue: events kobject_delayed_cleanup
| pstate: 60c00009 (nZCv daif +PAN +UAO)
| pc : debug_print_object+0x13c/0x1b0
| lr : debug_print_object+0x13c/0x1b0
| sp : ffffff83b2ec7970
| x29: ffffff83b2ec7970 x28: dfffffd000000000
| x27: ffffff83d674f000 x26: dfffffd000000000
| x25: ffffffd06b8fa660 x24: dfffffd000000000
| x23: 0000000000000000 x22: ffffffd06b7c5108
| x21: ffffffd06d597860 x20: ffffffd06e2c21c0
| x19: ffffffd06d5974c0 x18: 000000000001dad8
| x17: 0000000000000000 x16: dfffffd000000000
| BUG: KASAN: use-after-free in qcom_glink_rpdev_release+0x54/0x70
| x15: ffffffffffffffff x14: 79616c6564203a74
| x13: 0000000000000000 x12: 0000000000000080
| Write of size 8 at addr ffffff83d95768d0 by task kworker/3:1/150
| x11: 0000000000000001 x10: 0000000000000000
| x9 : fc9e8edec0ad0300 x8 : fc9e8edec0ad0300
|
| x7 : 0000000000000000 x6 : 0000000000000000
| x5 : 0000000000000080 x4 : 0000000000000000
| CPU: 3 PID: 150 Comm: kworker/3:1 Tainted: G        W         5.4.147-lockdep #1
| x3 : ffffffd06c149574 x2 : ffffff83f77f7498
| x1 : ffffffd06d596f60 x0 : 0000000000000061
| Hardware name: Google CoachZ (rev1 - 2) with LTE (DT)
| Call trace:
|  debug_print_object+0x13c/0x1b0
| Workqueue: events kobject_delayed_cleanup
|  __debug_check_no_obj_freed+0x25c/0x3c0
|  debug_check_no_obj_freed+0x18/0x20
| Call trace:
|  slab_free_freelist_hook+0xb4/0x1bc
|  kfree+0xe8/0x2d8
|  dump_backtrace+0x0/0x27c
|  rpmsg_ctrldev_release_device+0x78/0xb8
|  device_release+0x68/0x14c
|  show_stack+0x20/0x2c
|  kobject_cleanup+0x12c/0x298
|  kobject_delayed_cleanup+0x10/0x18
|  dump_stack+0xe0/0x19c
|  process_one_work+0x578/0x92c
|  worker_thread+0x804/0xcf8
|  print_address_description+0x3c/0x4a8
|  kthread+0x2a8/0x314
|  ret_from_fork+0x10/0x18
|  __kasan_report+0x100/0x124

Signed-off-by: Sujit Kautkar <sujitka@...omium.org>
---
Changes in v3:
- Remove unecessary error check as per Matthias's comment

Changes in v2:
- Fix typo in commit message

 drivers/rpmsg/rpmsg_char.c | 10 ++--------
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/drivers/rpmsg/rpmsg_char.c b/drivers/rpmsg/rpmsg_char.c
index 876ce43df732b..a6a33155ca859 100644
--- a/drivers/rpmsg/rpmsg_char.c
+++ b/drivers/rpmsg/rpmsg_char.c
@@ -458,7 +458,7 @@ static void rpmsg_ctrldev_release_device(struct device *dev)
 
 	ida_simple_remove(&rpmsg_ctrl_ida, dev->id);
 	ida_simple_remove(&rpmsg_minor_ida, MINOR(dev->devt));
-	cdev_del(&ctrldev->cdev);
+	cdev_device_del(&ctrldev->cdev, &ctrldev->dev);
 	kfree(ctrldev);
 }
 
@@ -493,19 +493,13 @@ static int rpmsg_chrdev_probe(struct rpmsg_device *rpdev)
 	dev->id = ret;
 	dev_set_name(&ctrldev->dev, "rpmsg_ctrl%d", ret);
 
-	ret = cdev_add(&ctrldev->cdev, dev->devt, 1);
+	ret = cdev_device_add(&ctrldev->cdev, &ctrldev->dev);
 	if (ret)
 		goto free_ctrl_ida;
 
 	/* We can now rely on the release function for cleanup */
 	dev->release = rpmsg_ctrldev_release_device;
 
-	ret = device_add(dev);
-	if (ret) {
-		dev_err(&rpdev->dev, "device_add failed: %d\n", ret);
-		put_device(dev);
-	}
-
 	dev_set_drvdata(&rpdev->dev, ctrldev);
 
 	return ret;
-- 
2.31.0