Re: [PATCH 16/17] target/i386/sev: 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].
> 
> The sev_inject_launch_secret() passes @errp to error_prepend(), and as
> an APIs defined in target/i386/sev.h, it is necessary to protect its
> @errp with ERRP_GUARD().
> 
> To avoid the issue like [1] said, add missing ERRP_GUARD() at the
> beginning of this function.
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>       ("error: New macro ERRP_GUARD()").
> 
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   target/i386/sev.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/target/i386/sev.c b/target/i386/sev.c
> index 173de91afe7d..72930ff0dcc5 100644
> --- a/target/i386/sev.c
> +++ b/target/i386/sev.c
> @@ -1044,6 +1044,7 @@ sev_encrypt_flash(uint8_t *ptr, uint64_t len, Error **errp)
>   int sev_inject_launch_secret(const char *packet_hdr, const char *secret,
>                                uint64_t gpa, Error **errp)
>   {
> +    ERRP_GUARD();
>       struct kvm_sev_launch_secret input;
>       g_autofree guchar *data = NULL, *hdr = NULL;
>       int error, ret = 1;

Reviewed-by: Thomas Huth <thuth@redhat.com>