[PATCH] intel_th: Fix MSC output device reference leak

[Guangshuo Li]

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.

The reference is currently intended to be dropped from
intel_th_output_release(). However, a successful open replaces
file->f_op with the output driver's file operations before returning, so
close runs the output driver's release method rather than
intel_th_output_release().

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

Drop the device reference from intel_th_msc_release(), which is the
release path that is actually used for MSC output files.

Fixes: 95fc36a234da ("intel_th: fix device leak on output open()")
Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
---
 drivers/hwtracing/intel_th/msu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index a82cf74f39ad..84d99d7b1d20 100644
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -1490,8 +1490,10 @@ static int intel_th_msc_release(struct inode *inode, struct file *file)
 {
 	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;
 }
-- 
2.43.0