linux-kernel - [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure

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Message-Id: <20240229122250.24786-1-duoming@zju.edu.cn>
Date: Thu, 29 Feb 2024 20:22:50 +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,
	michal.simek@....com,
	sboyd@...nel.org,
	mturquette@...libre.com,
	Duoming Zhou <duoming@....edu.cn>
Subject: [PATCH v2] 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 adds 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 v2:
  - Use stack variable to replace kmalloc().

 drivers/clk/zynq/clkc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
index 7bdeaff2bfd..e4c4c9adf79 100644
--- a/drivers/clk/zynq/clkc.c
+++ b/drivers/clk/zynq/clkc.c
@@ -427,7 +427,7 @@ static void __init zynq_clk_setup(struct device_node *np)
 			SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock);
 
 	tmp = strlen("mio_clk_00x");
-	clk_name = kmalloc(tmp, GFP_KERNEL);
+	char clk_name[tmp];
 	for (i = 0; i < NUM_MIO_PINS; i++) {
 		int idx;
 
@@ -439,7 +439,6 @@ 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