clk: zynq: Prevent null pointer dereference caused by kmalloc failure

The kmalloc() in zynq_clk_setup() will return null if the
physical memory has run out. As a result, if we use snprintf()
to write data to the null address, the null pointer dereference
bug will happen.

This patch uses a stack variable to replace the kmalloc().

Fixes: 0ee52b157b8e ("clk: zynq: Add clock controller driver")
Suggested-by: Michal Simek <[e-mail]>
Suggested-by: Stephen Boyd <[e-mail]>
Signed-off-by: Duoming Zhou <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Acked-by: Michal Simek <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/zynq/clkc.c

···
 #define SLCR_SWDT_CLK_SEL		(zynq_clkc_base + 0x204)
 
 #define NUM_MIO_PINS	54
+#define CLK_NAME_LEN	16
 
 #define DBG_CLK_CTRL_CLKACT_TRC		BIT(0)
 #define DBG_CLK_CTRL_CPU_1XCLKACT	BIT(1)
···
 	int i;
 	u32 tmp;
 	int ret;
-	char *clk_name;
+	char clk_name[CLK_NAME_LEN];
 	unsigned int fclk_enable = 0;
 	const char *clk_output_name[clk_max];
 	const char *cpu_parents[4];
···
 			"gem1_emio_mux", CLK_SET_RATE_PARENT,
 			SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock);
 
-	tmp = strlen("mio_clk_00x");
-	clk_name = kmalloc(tmp, GFP_KERNEL);
 	for (i = 0; i < NUM_MIO_PINS; i++) {
 		int idx;
 
-		snprintf(clk_name, tmp, "mio_clk_%2.2d", i);
+		snprintf(clk_name, CLK_NAME_LEN, "mio_clk_%2.2d", i);
 		idx = of_property_match_string(np, "clock-names", clk_name);
 		if (idx >= 0)
 			can_mio_mux_parents[i] = of_clk_get_parent_name(np,
···
 		else
 			can_mio_mux_parents[i] = dummy_nm;
 	}
-	kfree(clk_name);
 	clk_register_mux(NULL, "can_mux", periph_parents, 4,
 			CLK_SET_RATE_NO_REPARENT, SLCR_CAN_CLK_CTRL, 4, 2, 0,
 			&canclk_lock);