Code: static int hi3660_stub_clk_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct resource *res;
	unsigned int i;
	int ret;

	/* Use mailbox client without blocking */
	stub_clk_chan.cl.dev = dev;
	stub_clk_chan.cl.tx_done = NULL;
	stub_clk_chan.cl.tx_block = false;
	stub_clk_chan.cl.knows_txdone = false;

	/* Allocate mailbox channel */
	stub_clk_chan.mbox = mbox_request_channel(&stub_clk_chan.cl, 0);
	if (IS_ERR(stub_clk_chan.mbox))
 		return PTR_ERR(stub_clk_chan.mbox);
 
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	freq_reg = devm_ioremap(dev, res->start, resource_size(res));
 	if (!freq_reg)
 		return -ENOMEM;

	freq_reg += HI3660_STUB_CLOCK_DATA;

	for (i = 0; i < HI3660_CLK_STUB_NUM; i++) {
		ret = devm_clk_hw_register(&pdev->dev, &hi3660_stub_clks[i].hw);
		if (ret)
			return ret;
	}

	return devm_of_clk_add_hw_provider(&pdev->dev, hi3660_stub_clk_hw_get,
					   hi3660_stub_clks);
}

Vulnerability Type: DoS 
CWE ID: CWE-476
Summary: The hi3660_stub_clk_probe function in drivers/clk/hisilicon/clk-hi3660-stub.c in the Linux kernel before 4.16 allows local users to cause a denial of service (NULL pointer dereference) by triggering a failure of resource retrieval.
Commit Message: clk: hisilicon: hi3660：Fix potential NULL dereference in hi3660_stub_clk_probe()

platform_get_resource() may return NULL, add proper check to
avoid potential NULL dereferencing.

This is detected by Coccinelle semantic patch.

@@
expression pdev, res, n, t, e, e1, e2;
@@

res = platform_get_resource(pdev, t, n);
+ if (!res)
+   return -EINVAL;
... when != res == NULL
e = devm_ioremap(e1, res->start, e2);

Fixes: 4f16f7ff3bc0 ("clk: hisilicon: Add support for Hi3660 stub clocks")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>