Re: [PATCH 14/16] hw/char/xen_console: Fix missing ERRP_GUARD() for error_prepend()

[Anthony PERARD <anthony.perard@cloud.com>]

On Thu, Feb 29, 2024 at 12:37:21AM +0800, 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 xen_console_connect() passes @errp to error_prepend() without
> ERRP_GUARD().
> 
> There're 2 places will call xen_console_connect():
>  - xen_console_realize(): the @errp is from DeviceClass.realize()'s
> 			  parameter.
>  - xen_console_frontend_changed(): the @errp points its caller's
>                                    @local_err.
> 
> To avoid the issue like [1] said, add missing ERRP_GUARD() at the
> beginning of xen_console_connect().
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>      ("error: New macro ERRP_GUARD()").
> 
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Anthony Perard <anthony.perard@citrix.com>
> Cc: Paul Durrant <paul@xen.org>
> Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>

Acked-by: Anthony PERARD <anthony.perard@citrix.com>

Thanks,

-- 
Anthony PERARD