Hi Rob,

On 05/16/18 21:19, frowand.l...@gmail.com wrote:
> From: Frank Rowand <frank.row...@sony.com>
> 
> The smatch static checker marks the data in offset as untrusted,
> leading it to warn:
> 
>   drivers/of/resolver.c:125 update_usages_of_a_phandle_reference()
>   error: buffer underflow 'prop->value' 's32min-s32max'
> 
> Add check to verify that offset is within the property data.
> 
> Reported-by: Dan Carpenter <dan.carpen...@oracle.com>
> Signed-off-by: Frank Rowand <frank.row...@sony.com>
> ---
>  drivers/of/resolver.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/of/resolver.c b/drivers/of/resolver.c
> index 65d0b7adfcd4..7edfac6f1914 100644
> --- a/drivers/of/resolver.c
> +++ b/drivers/of/resolver.c
> @@ -122,6 +122,11 @@ static int update_usages_of_a_phandle_reference(struct 
> device_node *overlay,
>                       goto err_fail;
>               }
>  
> +             if (offset < 0 || offset + sizeof(__be32) > prop->length) {
> +                     err = -EINVAL;
> +                     goto err_fail;
> +             }
> +
>               *(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
>       }
>  
> 

I should have mentioned that this results in a new compile warning
for W=2 and W=3.  The new if statement results in:

drivers/of/resolver.c:125:45: warning: comparison between signed and unsigned 
integer expressions [-Wsign-compare]

There are other pre-existing warnings in the same file for comparing
an integer to prop->length.  The correct solution is probably to
change the type of the length field in struct property to be
unsigned.  I have added that task to my todo list.

-Frank

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