Re: [PATCH] xen/ubsan: Fix UB in type_descriptor declaration

["Oleksii K." <oleksii.kurochko@xxxxxxxxx>]

On Mon, 2024-06-17 at 18:55 +0100, Andrew Cooper wrote:
> struct type_descriptor is arranged with a NUL terminated string
Should it be NULL instead of NUL?

> following the
> kind/info fields.
> 
> The only reason this doesn't trip UBSAN detection itself (on more
> modern
> compilers at least) is because struct type_descriptor is only
> referenced in
> suppressed regions.
> 
> Switch the declaration to be a real flexible member.  No functional
> change.
> 
> Fixes: 00fcf4dd8eb4 ("xen/ubsan: Import ubsan implementation from
> Linux 4.13")
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

~ Oleksii
> ---
> CC: George Dunlap <George.Dunlap@xxxxxxxxxx>
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
> CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> 
> For 4.19, and for backport to all reasonable versions.  This bug
> deserves some
> kind of irony award.
> ---
>  xen/common/ubsan/ubsan.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/common/ubsan/ubsan.h b/xen/common/ubsan/ubsan.h
> index a3159040fefb..3db42e75b138 100644
> --- a/xen/common/ubsan/ubsan.h
> +++ b/xen/common/ubsan/ubsan.h
> @@ -10,7 +10,7 @@ enum {
>  struct type_descriptor {
>       u16 type_kind;
>       u16 type_info;
> -     char type_name[1];
> +     char type_name[];
>  };
>  
>  struct source_location {
> 
> base-commit: 8b4243a9b560c89bb259db5a27832c253d4bebc7