[PATCH 4/5] perf: arm: pmu: fix reference leak on failed device registration

[Vastargazing]

When platform_device_register() fails in arm_acpi_register_pmu_device(),
the embedded struct device has already been initialized by
device_initialize() inside platform_device_register(). The error path
unregisters the GSI interrupt but returns without dropping the device
reference:

  arm_acpi_register_pmu_device()
    -> platform_device_register(pdev)
       -> device_initialize(&pdev->dev)   /* kref = 1 */
       -> platform_device_add(pdev)       /* fails */
    <- acpi_unregister_gsi() called, but kref still 1

Per platform_device_register() kernel-doc:

  NOTE: _Never_ directly free @pdev after calling this function, even if
  it returned an error! Always use platform_device_put() to give up the
  reference initialised in this function instead.

Fix this by calling platform_device_put() in the error branch before
unregistering the GSI.

Fixes: d24a0c7099b3 ("arm_pmu: acpi: spe: Add initial MADT/SPE probing")
Cc: stable at vger.kernel.org
Assisted-by: GitHub Copilot (Claude Sonnet 4.5)
Signed-off-by: Vastargazing <vebohr at gmail.com>
---
 drivers/perf/arm_pmu_acpi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
index e80f76d95e68..c2defbc32ad9 100644
--- a/drivers/perf/arm_pmu_acpi.c
+++ b/drivers/perf/arm_pmu_acpi.c
@@ -119,8 +119,10 @@ arm_acpi_register_pmu_device(struct platform_device *pdev, u8 len,
 
 	pdev->resource[0].start = irq;
 	ret = platform_device_register(pdev);
-	if (ret)
+	if (ret) {
+		platform_device_put(pdev);
 		acpi_unregister_gsi(gsi);
+	}
 
 	return ret;
 }
-- 
2.51.0