Re: [PATCH] btf: Protect BTF_KIND_INFO against invalid kind

[Will Hawkins <hawkinsw@obs.cr>]

On Mon, Jul 29, 2024 at 2:14 PM David Faust <david.faust@oracle.com> wrote:
>
>
> On 7/29/24 07:42, Will Hawkins wrote:
> > If the user provides a kind value that is more than 5 bits, the
> > BTF_KIND_INFO macro would emit incorrect values for info (by clobbering
> > values of the kind flag).
> >
> > Tested on x86_64-redhat-linux.
>
> OK, thanks.

Just let me know if there is anything else that you need from me!
Will

>
> >
> > include/ChangeLog:
> >
> >       * btf.h (BTF_TYPE_INFO): Protect against user providing invalid
> >         kind.
> >
> > Signed-off-by: Will Hawkins <hawkinsw@obs.cr>
> > ---
> >
> > Notes:
> >      I have a small out-of-tree test but was not sure whether a) it should
> >                be included and/or b) where it should be included. If you would
> >                like me to include it, please just let me know where it should go!
> >
> >  include/btf.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/btf.h b/include/btf.h
> > index 3f45ffb0b6b..0c3e1a1cf51 100644
> > --- a/include/btf.h
> > +++ b/include/btf.h
> > @@ -82,7 +82,7 @@ struct btf_type
> >    };
> >  };
> >
> > -/* The folloing macros access the information encoded in btf_type.info.  */
> > +/* The following macros access the information encoded in btf_type.info.  */
> >  /* Type kind. See below.  */
> >  #define BTF_INFO_KIND(info)  (((info) >> 24) & 0x1f)
> >  /* Number of entries of variable length data following certain type kinds.
> > @@ -95,7 +95,7 @@ struct btf_type
> >
> >  /* Encoding for struct btf_type.info.  */
> >  #define BTF_TYPE_INFO(kind, kflag, vlen) \
> > -  ((((kflag) ? 1 : 0 ) << 31) | ((kind) << 24) | ((vlen) & 0xffff))
> > +  ((((kflag) ? 1 : 0 ) << 31) | ((kind & 0x1f) << 24) | ((vlen) & 0xffff))
> >
> >  #define BTF_KIND_UNKN                0       /* Unknown or invalid.  */
> >  #define BTF_KIND_INT         1       /* Integer.  */