[PATCH 6.1 237/609] intel_th: fix MSC output device reference leak

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guangshuo Li <[email protected]>

commit 761b785a0cfbce43761227bc42a7f984f31f8921 upstream.

intel_th_output_open() looks up the output device with
bus_find_device_by_devt(), which returns the device with a reference that
must be dropped after use.

commit 95fc36a234da ("intel_th: fix device leak on output open()")
attempted to drop the reference from intel_th_output_release(). However,
a successful open replaces file->f_op with the output driver file
operations before returning, so close runs the output driver release
callback instead.

For MSC outputs, close runs intel_th_msc_release(), which only removes
the per-file iterator and does not drop the device reference taken by
intel_th_output_open(). Consequently, every successful MSC output open
leaks one device reference.

Drop the device reference from intel_th_msc_release(), which is the
release path actually used for MSC output files. Remove the now-unused
intel_th_output_release() callback from intel_th_output_fops.

Fixes: 95fc36a234da ("intel_th: fix device leak on output open()")
Cc: stable <[email protected]>
Signed-off-by: Guangshuo Li <[email protected]>
Reviewed-by: Johan Hovold <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/hwtracing/intel_th/core.c |   10 ----------
 drivers/hwtracing/intel_th/msu.c  |    2 ++
 2 files changed, 2 insertions(+), 10 deletions(-)

--- a/drivers/hwtracing/intel_th/core.c
+++ b/drivers/hwtracing/intel_th/core.c
@@ -843,18 +843,8 @@ out_put_device:
 	return err;
 }
 
-static int intel_th_output_release(struct inode *inode, struct file *file)
-{
-	struct intel_th_device *thdev = file->private_data;
-
-	put_device(&thdev->dev);
-
-	return 0;
-}
-
 static const struct file_operations intel_th_output_fops = {
 	.open	= intel_th_output_open,
-	.release = intel_th_output_release,
 	.llseek	= noop_llseek,
 };
 
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1477,8 +1477,10 @@ static int intel_th_msc_release(struct i
 {
 	struct msc_iter *iter = file->private_data;
 	struct msc *msc = iter->msc;
+	struct intel_th_device *thdev = msc->thdev;
 
 	msc_iter_remove(iter, msc);
+	put_device(&thdev->dev);
 
 	return 0;
 }