firmware: arm_scpi: Fix device_node reference leak in probe path

[ Upstream commit 879c001afb ]

A device_node reference obtained from the device tree is not released
on all error paths in the arm_scpi probe path. Specifically, a node
returned by of_parse_phandle() could be leaked when the probe failed
after the node was acquired. The probe function returns early and
the shmem reference is not released.

Use __free(device_node) scope-based cleanup to automatically release
the reference when the variable goes out of scope.

Fixes: ed7ecb8839 ("firmware: arm_scpi: Add compatibility checks for shmem node")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Message-Id: <20260121-arm_scpi_2-v2-1-702d7fa84acb@gmail.com>
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/firmware/arm_scpi.c

@@ -18,6 +18,7 @@
 
 #include <linux/bitmap.h>
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/export.h>
@@ -945,13 +946,13 @@ static int scpi_probe(struct platform_device *pdev)
 		int idx = scpi_drvinfo->num_chans;
 		struct scpi_chan *pchan = scpi_drvinfo->channels + idx;
 		struct mbox_client *cl = &pchan->cl;
-		struct device_node *shmem = of_parse_phandle(np, "shmem", idx);
+		struct device_node *shmem __free(device_node) =
+			of_parse_phandle(np, "shmem", idx);
 
 		if (!of_match_node(shmem_of_match, shmem))
 			return -ENXIO;
 
 		ret = of_address_to_resource(shmem, 0, &res);
-		of_node_put(shmem);
 		if (ret) {
 			dev_err(dev, "failed to get SCPI payload mem resource\n");
 			return ret;