| Message ID | 20240715095939.72492-2-zhao1.liu@intel.com |
|---|---|
| State | New |
| Headers | show |
On Mon, Jul 15, 2024 at 11:45 AM Zhao Liu <zhao1.liu@intel.com> wrote: > > As the comment in qapi/error, dereferencing @errp requires > ERRP_GUARD(): > > * = Why, when and how to use ERRP_GUARD() = > * > * Without ERRP_GUARD(), use of the @errp parameter is restricted: > * - It must not be dereferenced, because it may be null. > ... > * 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. > * > * Using it when it's not needed is safe, but please avoid cluttering > * the source with useless code. > > Though vhost_vdpa_device_realize() is called at DeviceClass.realize() > context and won't get NULL @errp, it's still better to follow the > requirement to add the ERRP_GUARD(). > > But qemu_open() and vhost_vdpa_device_get_u32()'s return values can > distinguish between successful and unsuccessful calls, so check the > return values directly without dereferencing @errp, which eliminates > the need of ERRP_GUARD(). > > Cc: "Michael S. Tsirkin" <mst@redhat.com> > Cc: "Eugenio Pérez" <eperezma@redhat.com> > Cc: Jason Wang <jasowang@redhat.com> > Signed-off-by: Zhao Liu <zhao1.liu@intel.com> > --- > hw/virtio/vdpa-dev.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c > index 64b96b226c39..7b439efdc1d3 100644 > --- a/hw/virtio/vdpa-dev.c > +++ b/hw/virtio/vdpa-dev.c > @@ -50,6 +50,7 @@ vhost_vdpa_device_get_u32(int fd, unsigned long int cmd, Error **errp) > > static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > { > + ERRP_GUARD(); Good catch, thank you! But removing the err dereferencing eliminates the need for ERRP_GUARD(), doesn't it? Thanks! > VirtIODevice *vdev = VIRTIO_DEVICE(dev); > VhostVdpaDevice *v = VHOST_VDPA_DEVICE(vdev); > struct vhost_vdpa_iova_range iova_range; > @@ -63,19 +64,19 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > } > > v->vhostfd = qemu_open(v->vhostdev, O_RDWR, errp); > - if (*errp) { > + if (v->vhostfd < 0) { > return; > } > > v->vdev_id = vhost_vdpa_device_get_u32(v->vhostfd, > VHOST_VDPA_GET_DEVICE_ID, errp); > - if (*errp) { > + if (v->vdev_id < 0) { > goto out; > } > > max_queue_size = vhost_vdpa_device_get_u32(v->vhostfd, > VHOST_VDPA_GET_VRING_NUM, errp); > - if (*errp) { > + if (max_queue_size < 0) { > goto out; > } > > @@ -89,7 +90,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > > v->num_queues = vhost_vdpa_device_get_u32(v->vhostfd, > VHOST_VDPA_GET_VQS_COUNT, errp); > - if (*errp) { > + if (v->num_queues < 0) { > goto out; > } > > @@ -127,7 +128,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > v->config_size = vhost_vdpa_device_get_u32(v->vhostfd, > VHOST_VDPA_GET_CONFIG_SIZE, > errp); > - if (*errp) { > + if (v->config_size < 0) { > goto vhost_cleanup; > } > > -- > 2.34.1 >
On Mon, Jul 15, 2024 at 11:01:08PM +0200, Eugenio Perez Martin wrote: > Date: Mon, 15 Jul 2024 23:01:08 +0200 > From: Eugenio Perez Martin <eperezma@redhat.com> > Subject: Re: [PATCH] hw/virtio/vdpa-dev: Check returned value instead of > dereferencing @errp > > On Mon, Jul 15, 2024 at 11:45 AM Zhao Liu <zhao1.liu@intel.com> wrote: > > > > As the comment in qapi/error, dereferencing @errp requires > > ERRP_GUARD(): > > > > * = Why, when and how to use ERRP_GUARD() = > > * > > * Without ERRP_GUARD(), use of the @errp parameter is restricted: > > * - It must not be dereferenced, because it may be null. > > ... > > * 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. > > * > > * Using it when it's not needed is safe, but please avoid cluttering > > * the source with useless code. > > > > Though vhost_vdpa_device_realize() is called at DeviceClass.realize() > > context and won't get NULL @errp, it's still better to follow the > > requirement to add the ERRP_GUARD(). > > > > But qemu_open() and vhost_vdpa_device_get_u32()'s return values can > > distinguish between successful and unsuccessful calls, so check the > > return values directly without dereferencing @errp, which eliminates > > the need of ERRP_GUARD(). > > > > Cc: "Michael S. Tsirkin" <mst@redhat.com> > > Cc: "Eugenio Pérez" <eperezma@redhat.com> > > Cc: Jason Wang <jasowang@redhat.com> > > Signed-off-by: Zhao Liu <zhao1.liu@intel.com> > > --- > > hw/virtio/vdpa-dev.c | 11 ++++++----- > > 1 file changed, 6 insertions(+), 5 deletions(-) > > > > diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c > > index 64b96b226c39..7b439efdc1d3 100644 > > --- a/hw/virtio/vdpa-dev.c > > +++ b/hw/virtio/vdpa-dev.c > > @@ -50,6 +50,7 @@ vhost_vdpa_device_get_u32(int fd, unsigned long int cmd, Error **errp) > > > > static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > > { > > + ERRP_GUARD(); > > Good catch, thank you! But removing the err dereferencing eliminates > the need for ERRP_GUARD(), doesn't it? > Thanks Eugenio! You're right and I forgot to delete it. I'll post a new version.
On Tue, Jul 16, 2024 at 5:05 AM Zhao Liu <zhao1.liu@intel.com> wrote: > > On Mon, Jul 15, 2024 at 11:01:08PM +0200, Eugenio Perez Martin wrote: > > Date: Mon, 15 Jul 2024 23:01:08 +0200 > > From: Eugenio Perez Martin <eperezma@redhat.com> > > Subject: Re: [PATCH] hw/virtio/vdpa-dev: Check returned value instead of > > dereferencing @errp > > > > On Mon, Jul 15, 2024 at 11:45 AM Zhao Liu <zhao1.liu@intel.com> wrote: > > > > > > As the comment in qapi/error, dereferencing @errp requires > > > ERRP_GUARD(): > > > > > > * = Why, when and how to use ERRP_GUARD() = > > > * > > > * Without ERRP_GUARD(), use of the @errp parameter is restricted: > > > * - It must not be dereferenced, because it may be null. > > > ... > > > * 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. > > > * > > > * Using it when it's not needed is safe, but please avoid cluttering > > > * the source with useless code. > > > > > > Though vhost_vdpa_device_realize() is called at DeviceClass.realize() > > > context and won't get NULL @errp, it's still better to follow the > > > requirement to add the ERRP_GUARD(). > > > > > > But qemu_open() and vhost_vdpa_device_get_u32()'s return values can > > > distinguish between successful and unsuccessful calls, so check the > > > return values directly without dereferencing @errp, which eliminates > > > the need of ERRP_GUARD(). > > > > > > Cc: "Michael S. Tsirkin" <mst@redhat.com> > > > Cc: "Eugenio Pérez" <eperezma@redhat.com> > > > Cc: Jason Wang <jasowang@redhat.com> > > > Signed-off-by: Zhao Liu <zhao1.liu@intel.com> > > > --- > > > hw/virtio/vdpa-dev.c | 11 ++++++----- > > > 1 file changed, 6 insertions(+), 5 deletions(-) > > > > > > diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c > > > index 64b96b226c39..7b439efdc1d3 100644 > > > --- a/hw/virtio/vdpa-dev.c > > > +++ b/hw/virtio/vdpa-dev.c > > > @@ -50,6 +50,7 @@ vhost_vdpa_device_get_u32(int fd, unsigned long int cmd, Error **errp) > > > > > > static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) > > > { > > > + ERRP_GUARD(); > > > > Good catch, thank you! But removing the err dereferencing eliminates > > the need for ERRP_GUARD(), doesn't it? > > > > Thanks Eugenio! You're right and I forgot to delete it. I'll post a new > version. > > Good! With that removed, Acked-by: Eugenio Pérez <eperezma@redhat.com> Thanks!
diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c index 64b96b226c39..7b439efdc1d3 100644 --- a/hw/virtio/vdpa-dev.c +++ b/hw/virtio/vdpa-dev.c @@ -50,6 +50,7 @@ vhost_vdpa_device_get_u32(int fd, unsigned long int cmd, Error **errp) static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) { + ERRP_GUARD(); VirtIODevice *vdev = VIRTIO_DEVICE(dev); VhostVdpaDevice *v = VHOST_VDPA_DEVICE(vdev); struct vhost_vdpa_iova_range iova_range; @@ -63,19 +64,19 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) } v->vhostfd = qemu_open(v->vhostdev, O_RDWR, errp); - if (*errp) { + if (v->vhostfd < 0) { return; } v->vdev_id = vhost_vdpa_device_get_u32(v->vhostfd, VHOST_VDPA_GET_DEVICE_ID, errp); - if (*errp) { + if (v->vdev_id < 0) { goto out; } max_queue_size = vhost_vdpa_device_get_u32(v->vhostfd, VHOST_VDPA_GET_VRING_NUM, errp); - if (*errp) { + if (max_queue_size < 0) { goto out; } @@ -89,7 +90,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) v->num_queues = vhost_vdpa_device_get_u32(v->vhostfd, VHOST_VDPA_GET_VQS_COUNT, errp); - if (*errp) { + if (v->num_queues < 0) { goto out; } @@ -127,7 +128,7 @@ static void vhost_vdpa_device_realize(DeviceState *dev, Error **errp) v->config_size = vhost_vdpa_device_get_u32(v->vhostfd, VHOST_VDPA_GET_CONFIG_SIZE, errp); - if (*errp) { + if (v->config_size < 0) { goto vhost_cleanup; }
As the comment in qapi/error, dereferencing @errp requires ERRP_GUARD(): * = Why, when and how to use ERRP_GUARD() = * * Without ERRP_GUARD(), use of the @errp parameter is restricted: * - It must not be dereferenced, because it may be null. ... * 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. * * Using it when it's not needed is safe, but please avoid cluttering * the source with useless code. Though vhost_vdpa_device_realize() is called at DeviceClass.realize() context and won't get NULL @errp, it's still better to follow the requirement to add the ERRP_GUARD(). But qemu_open() and vhost_vdpa_device_get_u32()'s return values can distinguish between successful and unsuccessful calls, so check the return values directly without dereferencing @errp, which eliminates the need of ERRP_GUARD(). Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: "Eugenio Pérez" <eperezma@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Signed-off-by: Zhao Liu <zhao1.liu@intel.com> --- hw/virtio/vdpa-dev.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)