[PATCH] of: fdt: fix overflow caused by fdt_prop extending beyond fdt

[PATCH] of: fdt: fix overflow caused by fdt_prop extending beyond fdt

[Abdelrahman Youssef]

While parsing FDT, fdt_prop sometimes extends beyond FDT resulting in
heap-overflow.

dt_ptr_ok() checks a pointer is within bounds of the FDT, so we can use it
here to fix the issue.

Suggested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Abdelrahman Youssef <abdelrahmanyossef12@gmail.com>
---
 drivers/of/fdt.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 75af1844f3..a756483578 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -257,6 +257,11 @@ static struct device_node *__of_unflatten_dtb(const void *infdt, int size,
 
 		case FDT_PROP:
 			fdt_prop = infdt + dt_struct;
+			if (dt_ptr_ok(fdt, fdt_prop)) {
+				ret = -ESPIPE;
+				goto err;
+			}
+
 			len = fdt32_to_cpu(fdt_prop->len);
 			nodep = fdt_prop->data;
 
-- 
2.43.0

Re: [PATCH] of: fdt: fix overflow caused by fdt_prop extending beyond fdt

[Ahmad Fatoum]

On 19.11.24 19:35, Abdelrahman Youssef wrote:
> While parsing FDT, fdt_prop sometimes extends beyond FDT resulting in
> heap-overflow.
> 
> dt_ptr_ok() checks a pointer is within bounds of the FDT, so we can use it
> here to fix the issue.
> 
> Suggested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> Signed-off-by: Abdelrahman Youssef <abdelrahmanyossef12@gmail.com>
> ---
>  drivers/of/fdt.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 75af1844f3..a756483578 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -257,6 +257,11 @@ static struct device_node *__of_unflatten_dtb(const void *infdt, int size,
>  
>  		case FDT_PROP:
>  			fdt_prop = infdt + dt_struct;
> +			if (dt_ptr_ok(fdt, fdt_prop)) {

Shouldn't you invert the condition?

Cheers,
Ahmad

> +				ret = -ESPIPE;
> +				goto err;
> +			}
> +
>  			len = fdt32_to_cpu(fdt_prop->len);
>  			nodep = fdt_prop->data;
>  


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Re: [PATCH] of: fdt: fix overflow caused by fdt_prop extending beyond fdt

[AbdelRahman Yossef]

Yes, It should be inverted.
I will send a v2.

Sorry for the inconvenience.

Cheers,
Abdelrahman