pstore/ram: Avoid allocation and leak of platform data

commit 5631e857 upstream.

Yue Hu noticed that when parsing device tree the allocated platform data
was never freed. Since it's not used beyond the function scope, this
switches to using a stack variable instead.
Reported-by: Yue Hu <huyue2@yulong.com>
Fixes: 35da6094 ("pstore/ram: add Device Tree bindings")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/pstore/ram.c

@@ -711,18 +711,15 @@ static int ramoops_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct ramoops_platform_data *pdata = dev->platform_data;
+	struct ramoops_platform_data pdata_local;
 	struct ramoops_context *cxt = &oops_cxt;
 	size_t dump_mem_sz;
 	phys_addr_t paddr;
 	int err = -EINVAL;
 
 	if (dev_of_node(dev) && !pdata) {
-		pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
-		if (!pdata) {
-			pr_err("cannot allocate platform data buffer\n");
-			err = -ENOMEM;
-			goto fail_out;
-		}
+		pdata = &pdata_local;
+		memset(pdata, 0, sizeof(*pdata));
 
 		err = ramoops_parse_dt(pdev, pdata);
 		if (err < 0)