dmirror_device_init() calls device_initialize() which sets the device
reference count to 1, but fails to call put_device() when error occurs
after dev_set_name() or cdev_device_add() failures. This results in
memory leaks of struct device objects. Additionally,
dmirror_device_remove() lacks the final put_device() call to properly
release the device reference.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 6a760f58c792 ("mm/hmm/test: use char dev with struct device to get device node")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 lib/test_hmm.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 83e3d8208a54..5159fc36eea6 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1458,20 +1458,25 @@ static int dmirror_device_init(struct dmirror_device *mdevice, int id)
 
 	ret = dev_set_name(&mdevice->device, "hmm_dmirror%u", id);
 	if (ret)
-		return ret;
+		goto put_device;
 
 	ret = cdev_device_add(&mdevice->cdevice, &mdevice->device);
 	if (ret)
-		return ret;
+		goto put_device;
 
 	/* Build a list of free ZONE_DEVICE struct pages */
 	return dmirror_allocate_chunk(mdevice, NULL);
+
+put_device:
+	put_device(&mdevice->device);
+	return ret;
 }
 
 static void dmirror_device_remove(struct dmirror_device *mdevice)
 {
 	dmirror_device_remove_chunks(mdevice);
 	cdev_device_del(&mdevice->cdevice, &mdevice->device);
+	put_device(&mdevice->device);
 }
 
 static int __init hmm_dmirror_init(void)
-- 
2.17.1

…
> dmirror_device_remove() lacks the final put_device() call to properly
> release the device reference.
…

See also once more:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.18-rc4#n94

Regards,
Markus