2024-02-14 07:42:47

by Duoming Zhou

Subject: [PATCH] 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.

The required memory is only 11 bytes, so this patch
adds a "__GFP_NOFAIL" flag in kmalloc in order that
the kmalloc will never return with failure.

Fixes: 0ee52b157b8e ("clk: zynq: Add clock controller driver")
Signed-off-by: Duoming Zhou <[email protected]>
---
drivers/clk/zynq/clkc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
index 7bdeaff2bfd..7621c2f0046 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);
+ clk_name = kmalloc(tmp, GFP_KERNEL | __GFP_NOFAIL);
for (i = 0; i < NUM_MIO_PINS; i++) {
int idx;

--
2.17.1

2024-02-19 13:48:02

by Michal Simek

Subject: Re: [PATCH] clk: zynq: Prevent null pointer dereference caused by kmalloc failure

On 2/14/24 08:33, Duoming Zhou wrote:
> 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.
>
> The required memory is only 11 bytes, so this patch
> adds a "__GFP_NOFAIL" flag in kmalloc in order that
> the kmalloc will never return with failure.
>
> Fixes: 0ee52b157b8e ("clk: zynq: Add clock controller driver")
> Signed-off-by: Duoming Zhou <[email protected]>
> ---
> drivers/clk/zynq/clkc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
> index 7bdeaff2bfd..7621c2f0046 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);
> + clk_name = kmalloc(tmp, GFP_KERNEL | __GFP_NOFAIL);
> for (i = 0; i < NUM_MIO_PINS; i++) {
> int idx;
>

Reviewed-by: Michal Simek <[email protected]>

Thanks,
Michal

2024-02-28 23:07:16

by Stephen Boyd

Subject: Re: [PATCH] clk: zynq: Prevent null pointer dereference caused by kmalloc failure

Quoting Duoming Zhou (2024-02-13 23:33:18)
> diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c
> index 7bdeaff2bfd..7621c2f0046 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);
> + clk_name = kmalloc(tmp, GFP_KERNEL | __GFP_NOFAIL);

Just make a stack variable please. __GFP_NOFAIL is a bad code smell.

> for (i = 0; i < NUM_MIO_PINS; i++) {
> int idx;
>