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

[David Faust <david.faust@oracle.com>]

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.

> 
> 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.  */