Re: [PATCH 17/17] target/s390x/cpu_models: Fix missing ERRP_GUARD() for error_prepend()

[Thomas Huth <thuth@redhat.com>]

On 29/02/2024 15.39, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@intel.com>
> 
> As the comment in qapi/error, passing @errp to error_prepend() requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> ...
> * - It should not be passed to error_prepend(), error_vprepend() or
> *   error_append_hint(), because that doesn't work with &error_fatal.
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> 
> ERRP_GUARD() could avoid the case when @errp is the pointer of
> error_fatal, the user can't see this additional information, because
> exit() happens in error_setg earlier than information is added [1].
> 
> In target/s390x/cpu_models.c, there're 2 functions passing @errp to
> error_prepend() without ERRP_GUARD():
> - check_compatibility()
> - s390_realize_cpu_model()
> 
> Though both their @errp parameters point to their callers' local @err
> virables and don't cause the issue as [1] said, to follow the
> requirement of @errp, also add missing ERRP_GUARD() at their beginning.
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>       ("error: New macro ERRP_GUARD()").
> 
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Richard Henderson <richard.henderson@linaro.org>
> Cc: Ilya Leoshkevich <iii@linux.ibm.com>
> Cc: Thomas Huth <thuth@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   target/s390x/cpu_models.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/target/s390x/cpu_models.c b/target/s390x/cpu_models.c
> index a63d990e4e8e..1a1c09612271 100644
> --- a/target/s390x/cpu_models.c
> +++ b/target/s390x/cpu_models.c
> @@ -503,6 +503,7 @@ static void error_prepend_missing_feat(const char *name, void *opaque)
>   static void check_compatibility(const S390CPUModel *max_model,
>                                   const S390CPUModel *model, Error **errp)
>   {
> +    ERRP_GUARD();
>       S390FeatBitmap missing;
>   
>       if (model->def->gen > max_model->def->gen) {
> @@ -566,6 +567,7 @@ S390CPUModel *get_max_cpu_model(Error **errp)
>   
>   void s390_realize_cpu_model(CPUState *cs, Error **errp)
>   {
> +    ERRP_GUARD();
>       Error *err = NULL;

I think that function could use an additional clean-up now: Remove the local 
"err" variable and use "errp" only instead.

  Thomas


>       S390CPUClass *xcc = S390_CPU_GET_CLASS(cs);
>       S390CPU *cpu = S390_CPU(cs);