[PATCH v3] bsps/shared/ofw: Fix coverity reported defects

[Niteesh G. S.]

On Thu, Feb 4, 2021 at 1:21 AM Gedare Bloom <gedare at rtems.org> wrote:

>
>
> On Wed, Feb 3, 2021 at 2:48 AM G S Niteesh Babu <niteesh.gs at gmail.com>
> wrote:
>
>> Fixed use after free and null pointer dereference defects
>>
>> FIXES:
>> 1) CID 1472601 (NULL_RETURNS)
>> 2) CID 1472600 (USE_AFTER_FREE)
>> 3) CID 1472599 (USE_AFTER_FREE)
>> 4) CID 1472598 (USE_AFTER_FREE)
>> 5) CID 1472596 (USE_AFTER_FREE)
>> 6) CID 1472597 (ARRAY_VS_SINGLETON)
>> 7) CID 1472595 (ARRAY_VS_SINGLETON)
>> ---
>>  bsps/shared/ofw/ofw.c | 36 ++++++++++++++++++------------------
>>  1 file changed, 18 insertions(+), 18 deletions(-)
>>
>> diff --git a/bsps/shared/ofw/ofw.c b/bsps/shared/ofw/ofw.c
>> index 82924b2600..ccd57e36af 100644
>> --- a/bsps/shared/ofw/ofw.c
>> +++ b/bsps/shared/ofw/ofw.c
>> @@ -313,7 +313,7 @@ ssize_t rtems_ofw_get_prop_alloc(
>>      }
>>
>>      if (rtems_ofw_get_prop(node, propname, *buf, len) == -1) {
>> -      rtems_ofw_free(buf);
>> +      rtems_ofw_free(*buf);
>>        *buf = NULL;
>>        return -1;
>>      }
>> @@ -344,7 +344,7 @@ ssize_t rtems_ofw_get_prop_alloc_multi(
>>      }
>>
>>      if (rtems_ofw_get_prop(node, propname, *buf, len) == -1) {
>> -      rtems_ofw_free(buf);
>> +      rtems_ofw_free(*buf);
>>        *buf = NULL;
>>        return -1;
>>      }
>> @@ -373,7 +373,7 @@ ssize_t rtems_ofw_get_enc_prop_alloc(
>>      }
>>
>>      if (rtems_ofw_get_enc_prop(node, propname, *buf, len) == -1) {
>> -      rtems_ofw_free(buf);
>> +      rtems_ofw_free(*buf);
>>        *buf = NULL;
>>        return -1;
>>      }
>> @@ -404,7 +404,7 @@ ssize_t rtems_ofw_get_enc_prop_alloc_multi(
>>      }
>>
>>      if (rtems_ofw_get_enc_prop(node, propname, *buf, len) == -1) {
>> -      rtems_ofw_free(buf);
>> +      rtems_ofw_free(*buf);
>>        *buf = NULL;
>>        return -1;
>>      }
>>
> The above all look fine to me.
>
>
>> @@ -500,21 +500,21 @@ static phandle_t rtems_ofw_get_effective_phandle(
>>  )
>>  {
>>    phandle_t child;
>> -  phandle_t ref;
>> +  phandle_t ref[1];
>>
>>
> I don't like this. I know this was suggested, but I think it is a little
> ridiculous. This is a false positive since we know that sizeof(*buf) ==
> len. I don't know if we can make that an assertion. Otherwise, we can just
> mark this as a false positive in coverity. We know the array dereference in
> this case won't overwrite past the bounds of ref.
>
> Instead of using hard-coded values of 4 in rtems_ofw_get_enc_prop() you
> might make it more explicitly using sizeof(pcell_t), since that is what you
> mean.
>
Done.

>
> I would also agree to change the strncpy as Christian identified before in
> rtems_ofw_get_prop().
>
Is the reason to avoid strncpy that it ignores the null byte if len(dst) <=
len(src)?
If so can I do an explicit null byte append?
Or is there any other reason?


>
>>    for (child = rtems_ofw_child(node); child != 0; child =
>> rtems_ofw_peer(child)) {
>> -    ref = rtems_ofw_get_effective_phandle(child, xref);
>> -    if (ref != -1)
>> -      return ref;
>> +    ref[0] = rtems_ofw_get_effective_phandle(child, xref);
>>
>
> I didn't notice before, but is this recursion bounded (yes, it is a
> tree, but it might be better to rewrite this function non-recursively).
>
Just curious why is it better? Is it because it might use a lot of stack
frames?
I can only think of using stack or queue to implement it non-recursively.
Is there
any other way?

>
>
>> +    if (ref[0] != -1)
>> +      return ref[0];
>>
>> -    if (rtems_ofw_get_enc_prop(child, "phandle", &ref, sizeof(ref)) ==
>> -1 &&
>> -        rtems_ofw_get_enc_prop(child, "ibm,phandle", &ref, sizeof(ref))
>> == -1 &&
>> -        rtems_ofw_get_enc_prop(child, "linux,phandle", &ref,
>> sizeof(ref)) == -1
>> +    if (rtems_ofw_get_enc_prop(child, "phandle", ref, sizeof(ref)) == -1
>> &&
>> +        rtems_ofw_get_enc_prop(child, "ibm,phandle", ref, sizeof(ref))
>> == -1 &&
>> +        rtems_ofw_get_enc_prop(child, "linux,phandle", ref, sizeof(ref))
>> == -1
>>      ) {
>>        continue;
>>      }
>>
>> -    if (ref == xref)
>> +    if (ref[0] == xref)
>>        return child;
>>    }
>>
>> @@ -533,16 +533,16 @@ phandle_t rtems_ofw_node_from_xref( phandle_t xref )
>>
>>  phandle_t rtems_ofw_xref_from_node( phandle_t node )
>>  {
>> -  phandle_t ref;
>> +  phandle_t ref[1];
>>
>> -    if (rtems_ofw_get_enc_prop(node, "phandle", &ref, sizeof(ref)) == -1
>> &&
>> -        rtems_ofw_get_enc_prop(node, "ibm,phandle", &ref, sizeof(ref))
>> == -1 &&
>> -        rtems_ofw_get_enc_prop(node, "linux,phandle", &ref, sizeof(ref))
>> == -1)
>> +    if (rtems_ofw_get_enc_prop(node, "phandle", ref, sizeof(ref)) == -1
>> &&
>> +        rtems_ofw_get_enc_prop(node, "ibm,phandle", ref, sizeof(ref)) ==
>> -1 &&
>> +        rtems_ofw_get_enc_prop(node, "linux,phandle", ref, sizeof(ref))
>> == -1)
>>      {
>>        return node;
>>      }
>>
>> -    return ref;
>> +    return ref[0];
>>  }
>>
>>  phandle_t rtems_ofw_instance_to_package( ihandle_t instance )
>> @@ -614,7 +614,7 @@ int rtems_ofw_get_reg(
>>      offset = rtems_fdt_phandle_to_offset(parent);
>>      ptr = fdt_getprop(fdtp, offset, "ranges", &len);
>>
>> -    if (len < 0) {
>> +    if (ptr == NULL) {
>>        break;
>>      }
>>
>> --
>> 2.17.1
>>
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>> devel at rtems.org
>> http://lists.rtems.org/mailman/listinfo/devel
>>
>
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