perf: arm_cspmu: fix error handling in arm_cspmu_impl_unregister()

commit 970e1e4 upstream.

driver_find_device() calls get_device() to increment the reference
count once a matching device is found. device_release_driver()
releases the driver, but it does not decrease the reference count that
was incremented by driver_find_device(). At the end of the loop, there
is no put_device() to balance the reference count. To avoid reference
count leakage, add put_device() to decrease the reference count.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: bfc653a ("perf: arm_cspmu: Separate Arm and vendor module")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Ma Ke

drivers/perf/arm_cspmu/arm_cspmu.c

@@ -1365,8 +1365,10 @@ void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match *impl_match)
 
 	/* Unbind the driver from all matching backend devices. */
 	while ((dev = driver_find_device(&arm_cspmu_driver.driver, NULL,
-			match, arm_cspmu_match_device)))
+			match, arm_cspmu_match_device))) {
 		device_release_driver(dev);
+		put_device(dev);
+	}
 
 	mutex_lock(&arm_cspmu_lock);