Re: [PATCH 09/46] error: Avoid error_propagate() after migrate_add_blocker()

[Vladimir Sementsov-Ogievskiy]

24.06.2020 19:43, Markus Armbruster wrote:

When migrate_add_blocker(blocker, &errp) is followed by
error_propagate(errp, err), we can often just as well do
migrate_add_blocker(..., errp).

Do that with this Coccinelle script:

     @@
     expression blocker, err, errp;
     expression ret;
     @@
     -    ret = migrate_add_blocker(blocker, &err);
     -    if (err) {
     +    ret = migrate_add_blocker(blocker, errp);
     +    if (ret < 0) {
             ... when != err;
     -        error_propagate(errp, err);
             ...
         }

     @@
     expression blocker, err, errp;
     @@
     -    migrate_add_blocker(blocker, &err);
     -    if (err) {
     +    if (migrate_add_blocker(blocker, errp) < 0) {
             ... when != err;
     -        error_propagate(errp, err);
             ...
         }

Double-check @err is not used afterwards.  Dereferencing it would be
use after free, but checking whether it's null would be legitimate.

Signed-off-by: Markus Armbruster <arm...@redhat.com>
---
  block/parallels.c            | 5 ++---
  block/qcow.c                 | 6 ++----
  block/vdi.c                  | 6 ++----
  block/vhdx.c                 | 5 ++---
  block/vmdk.c                 | 6 ++----
  block/vpc.c                  | 5 ++---
  block/vvfat.c                | 5 ++---
  hw/display/virtio-gpu-base.c | 5 +----
  hw/intc/arm_gic_kvm.c        | 4 +---
  hw/intc/arm_gicv3_its_kvm.c  | 4 +---
  hw/intc/arm_gicv3_kvm.c      | 4 +---
  hw/misc/ivshmem.c            | 4 +---
  hw/scsi/vhost-scsi.c         | 4 +---
  13 files changed, 20 insertions(+), 43 deletions(-)

[..]

diff --git a/hw/intc/arm_gicv3_its_kvm.c b/hw/intc/arm_gicv3_its_kvm.c
index ad0ebabc87..87bc4aeca1 100644
--- a/hw/intc/arm_gicv3_its_kvm.c
+++ b/hw/intc/arm_gicv3_its_kvm.c
@@ -113,9 +113,7 @@ static void kvm_arm_its_realize(DeviceState *dev, Error 
**errp)

Remove unused local_err

with fixed:
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>

          GITS_CTLR)) {
          error_setg(&s->migration_blocker, "This operating system kernel "
                     "does not support vITS migration");
-        migrate_add_blocker(s->migration_blocker, &local_err);
-        if (local_err) {
-            error_propagate(errp, local_err);
+        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
              error_free(s->migration_blocker);
              return;
          }

[..]


--
Best regards,
Vladimir