[Spice-devel] [PATCH spice-common 4/4] codegen: Check validity of array members

[Uri Lublin]

On 8/13/19 7:56 PM, Frediano Ziglio wrote:
> Check that combination of fields for an array does not
> lead to unsafe code.
> check_valid method came from generate_c_declaration with
> some more check and it's use in demarshaller to validate
> the array if the structure is not generated.
> 
> Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
> ---
>   python_modules/demarshal.py |  2 ++
>   python_modules/ptypes.py    | 18 +++++++++++++++++-
>   2 files changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/python_modules/demarshal.py b/python_modules/demarshal.py
> index acd4b6f..3736976 100644
> --- a/python_modules/demarshal.py
> +++ b/python_modules/demarshal.py
> @@ -315,6 +315,8 @@ def write_validate_pointer_item(writer, container, item, scope, parent_scope, st
>   def write_validate_array_item(writer, container, item, scope, parent_scope, start,
>                                 want_nw_size, want_mem_size, want_extra_size):
>       array = item.type
> +    if item.member:
> +        array.check_valid(item.member)
>       is_byte_size = False
>       element_type = array.element_type
>       if array.is_bytes_length():
> diff --git a/python_modules/ptypes.py b/python_modules/ptypes.py
> index 311ce3d..7a23bca 100644
> --- a/python_modules/ptypes.py
> +++ b/python_modules/ptypes.py
> @@ -485,7 +485,23 @@ class ArrayType(Type):
>       def c_type(self):
>           return self.element_type.c_type()
>   

Would be nice to add a comment saying what checks are made.
(Even though there are not many comments
> +    def check_valid(self, member):
> +        if member.has_attr("chunk") or member.has_attr("as_ptr"):
> +            return
> +        if member.has_attr("to_ptr") or member.has_attr("ptr_array"):

Does 'to_ptr' have identifier/constant_length ?  It's just a pointer.


Uri.

> +            if not (self.is_identifier_length() or self.is_constant_length()):
> +                raise Exception("Unsecure, no length of array")
> +            return
> +        if member.has_end_attr():
> +            return
> +        if self.is_remaining_length():
> +            raise Exception('C output array is not allocated')
> +        if self.is_constant_length() or self.is_identifier_length():
> +            return
> +        raise NotImplementedError('unknown array %s' % str(self))
> +
>       def generate_c_declaration(self, writer, member):
> +        self.check_valid(member)
>           name = member.name
>           if member.has_attr("chunk"):
>               return writer.writeln('SpiceChunks *%s;' % name)
> @@ -497,7 +513,7 @@ class ArrayType(Type):
>               return writer.writeln('%s *%s;' % (self.c_type(), name))
>           if member.has_attr("ptr_array"):
>               return writer.writeln('%s *%s[0];' % (self.c_type(), name))
> -        if member.has_end_attr() or self.is_remaining_length():
> +        if member.has_end_attr():
>               return writer.writeln('%s %s[0];' % (self.c_type(), name))
>           if self.is_constant_length():
>               return writer.writeln('%s %s[%s];' % (self.c_type(), name, self.size))
>