linux-kernel - [PATCH v3] clk: zynq: Prevent null pointer dereference caused by kmalloc failure

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Message-Id: <20240301070336.13700-1-duoming@zju.edu.cn>
Date: Fri,  1 Mar 2024 15:03:36 +0800
From: Duoming Zhou <duoming@....edu.cn>
To: linux-kernel@...r.kernel.org
Cc: linux-arm-kernel@...ts.infradead.org,
	linux-clk@...r.kernel.org,
	mturquette@...libre.com,
	sboyd@...nel.org,
	michal.simek@....com,
	Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH v3] 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")
Signed-off-by: Duoming Zhou <duoming@....edu.cn>
---
Changes in v3:
  - Put stack variable in the head of the function and remove variable tmp.

 drivers/clk/zynq/clkc.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
index 7bdeaff2bfd..45479653c3b 100644
--- a/drivers/clk/zynq/clkc.c
+++ b/drivers/clk/zynq/clkc.c
@@ -215,7 +215,7 @@ static void __init zynq_clk_setup(struct device_node *np)
 	int i;
 	u32 tmp;
 	int ret;
-	char *clk_name;
+	char clk_name[16];
 	unsigned int fclk_enable = 0;
 	const char *clk_output_name[clk_max];
 	const char *cpu_parents[4];
@@ -426,12 +426,10 @@ static void __init zynq_clk_setup(struct device_node *np)
 			"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, 16, "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,
@@ -439,7 +437,6 @@ static void __init zynq_clk_setup(struct device_node *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);
-- 
2.17.1