Re: [Xen-devel] [PATCH v6 3/6] xen: Introduce a helper to read a u32 property in device tree.

[Chen Baozi <baozich@xxxxxxxxx>]

On Aug 13, 2013, at 6:19 AM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:

> On 12 August 2013 16:19, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
>> On 08/09/2013 03:20 AM, Chen Baozi wrote:
>>> Signed-off-by: Chen Baozi <baozich@xxxxxxxxx>
>> Acked-by: Julien Grall <julien.grall@xxxxxxxxxx>
>>> ---
>>> xen/common/device_tree.c      | 15 +++++++++++++++
>>> xen/include/xen/device_tree.h | 11 +++++++++++
>>> 2 files changed, 26 insertions(+)
>>> 
>>> diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c
>>> index 84d704d..a4701eb 100644
>>> --- a/xen/common/device_tree.c
>>> +++ b/xen/common/device_tree.c
>>> @@ -574,6 +574,21 @@ const void *dt_get_property(const struct 
>>> dt_device_node *np,
>>>     return pp ? pp->value : NULL;
>>> }
>>> 
>>> +bool_t dt_property_read_u32(const struct dt_device_node *np,
>>> +                         const char *name, u32 *out_value)
>>> +{
>>> +    u32 len;
>>> +    const __be32 *val;
>>> +
>>> +    val = dt_get_property(np, name, &len);
>>> +    if ( !val || len > sizeof(*out_value) )
>>> +        return 0;
> 
> Hum .. I have just noticed that the check is wrong.
> Len must be greater or equal to sizeof (*out_value). Otherwise you can
> read random bytes.

Oops... I think I mixed up the "len" between linux codes and this.

Thanks for catching it out!

Baozi

> 
> 
>>> +
>>> +    *out_value = be32_to_cpup(val);
>>> +
>>> +    return 1;
>>> +}
>>> +
>>> bool_t dt_device_is_compatible(const struct dt_device_node *device,
>>>                                const char *compat)
>>> {
>>> diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
>>> index 5a2a5c6..faf727f 100644
>>> --- a/xen/include/xen/device_tree.h
>>> +++ b/xen/include/xen/device_tree.h
>>> @@ -300,6 +300,17 @@ const void *dt_get_property(const struct 
>>> dt_device_node *np,
>>>                             const char *name, u32 *lenp);
>>> 
>>> /**
>>> + * dt_property_read_u32 - Helper to read a u32 property.
>>> + * @np: node to get the value
>>> + * @name: name of the property
>>> + * @out_value: pointer to return value
>>> + *
>>> + * Return true if get the desired value.
>>> + */
>>> +bool_t dt_property_read_u32(const struct dt_device_node *np,
>>> +                            const char *name, u32 *out_value);
>>> +
>>> +/**
>>>  * Checks if the given "compat" string matches one of the strings in
>>>  * the device's "compatible" property
>>>  */
>>> 
>> 
>> 
>> --
>> Julien Grall
> 
> 
> 
> -- 
> Julien Grall


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