Re: [PATCH nft 7/9] expression: cleanup expr_ops_by_type() and handle u32 input

[Thomas Haller <thaller@redhat.com>]

On Wed, 2023-09-20 at 20:13 +0200, Pablo Neira Ayuso wrote:
> On Wed, Sep 20, 2023 at 04:26:08PM +0200, Thomas Haller wrote:
> > 
> > -const struct expr_ops *expr_ops_by_type(enum expr_types value)
> > +const struct expr_ops *expr_ops_by_type_u32(uint32_t value)
> >  {
> > -       /* value might come from unreliable source, such as "udata"
> > -        * annotation of set keys.  Avoid BUG() assertion.
> > -        */
> > -       if (value == EXPR_INVALID || value > EXPR_MAX)
> > +       if (value > (uint32_t) EXPR_MAX)
> 
> I think this still allows a third party to set EXPR_INVALID in the
> netlink userdata attribute, right?
> 
> >                 return NULL;
> > -
> >         return __expr_ops_by_type(value);
> >  }

Yes, it still allows that. It's handled by the following
__expr_ops_by_type(), which returns NULL for invalid types (like
EXPR_INVALID).

The check "if (value > (uint32_t) EXPR_MAX)" is only here to ensure
that nothing is lost while casting the uint32_t "value" to the enum
expr_types.


Thomas