[Spice-devel] [PATCH spice-common v2] codegen: Check validity of array members

[Frediano Ziglio]

ping

> 
> ping
> 
> > 
> > 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    | 31 ++++++++++++++++++++++++++++++-
> >  2 files changed, 32 insertions(+), 1 deletion(-)
> > 
> > Changes since v1:
> > - add comments to explain the checks done
> > 
> > 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..ebe001c 100644
> > --- a/python_modules/ptypes.py
> > +++ b/python_modules/ptypes.py
> > @@ -485,7 +485,36 @@ class ArrayType(Type):
> >      def c_type(self):
> >          return self.element_type.c_type()
> >  
> > +    def check_valid(self, member):
> > +        # These attribute corresponds to specific structure size
> > +        if member.has_attr("chunk") or member.has_attr("as_ptr"):
> > +            return
> > +        # These attribute indicate that the array is stored in the
> > structure
> > +        # as a pointer of the array. If there's no way to retrieve the
> > length
> > +        # of the array give error, as the user has no way to do bound
> > checks
> > +        if member.has_attr("to_ptr") or member.has_attr("ptr_array"):
> > +            if not (self.is_identifier_length() or
> > self.is_constant_length()):
> > +                raise Exception("Unsecure, no length of array")
> > +            return
> > +        # This attribute indicate that the array is store at the end
> > +        # of the structure, the user will compute the length from the
> > +        # entire message size
> > +        if member.has_end_attr():
> > +            return
> > +        # Avoid bug, the array has no length specified and no space
> > +        # would be allocated
> > +        if self.is_remaining_length():
> > +            raise Exception('C output array is not allocated')
> > +        # For constant length (like "foo[5]") the field is a sized array
> > +        # For identifier automatically a pointer to allocated data is
> > store,
> > +        # in this case user can read the size using the other field
> > specified
> > +        # by the identifier
> > +        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 +526,7 @@ 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))