Re: [PATCH 15/17] net/vhost-vdpa: 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 net_init_vhost_vdpa() passes @errp to error_prepend(), and as a
> member of net_client_init_fun[], it's called in net_client_init1() and
> gets @errp from this caller.
> 
> But because netdev_init_modern() passes &error_fatal to
> net_client_init1(), then @errp parameter of net_init_vhost_vdpa() would
> point to @error_fatal. This causes the error message in error_prepend()
> to be lost because of the above issue.
> 
> To fix this, 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: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
> ---
>   net/vhost-vdpa.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/net/vhost-vdpa.c b/net/vhost-vdpa.c
> index 3726ee5d6763..6c1fa396aae1 100644
> --- a/net/vhost-vdpa.c
> +++ b/net/vhost-vdpa.c
> @@ -1751,6 +1751,7 @@ static int vhost_vdpa_get_max_queue_pairs(int fd, uint64_t features,
>   int net_init_vhost_vdpa(const Netdev *netdev, const char *name,
>                           NetClientState *peer, Error **errp)
>   {
> +    ERRP_GUARD();
>       const NetdevVhostVDPAOptions *opts;
>       uint64_t features;
>       int vdpa_device_fd;

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