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

[Markus Armbruster <armbru@redhat.com>]

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 <armbru@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/block/parallels.c b/block/parallels.c
index a84ec6a518..860dbb80a2 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -862,9 +862,8 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The Parallels format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail;
     }
diff --git a/block/qcow.c b/block/qcow.c
index dca2a1fe7d..eefa3b63da 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -121,7 +121,6 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
     unsigned int len, i, shift;
     int ret;
     QCowHeader header;
-    Error *local_err = NULL;
     QCryptoBlockOpenOptions *crypto_opts = NULL;
     unsigned int cflags = 0;
     QDict *encryptopts = NULL;
@@ -314,9 +313,8 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The qcow format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail;
     }
diff --git a/block/vdi.c b/block/vdi.c
index 2f506a01ba..5fca67f52d 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -375,7 +375,6 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
     VdiHeader header;
     size_t bmap_size;
     int ret;
-    Error *local_err = NULL;
     QemuUUID uuid_link, uuid_parent;
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
@@ -496,9 +495,8 @@ static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vdi format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail_free_bmap;
     }
diff --git a/block/vhdx.c b/block/vhdx.c
index ac5a9094c4..b9ef4ff074 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1089,9 +1089,8 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vhdx format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail;
     }
diff --git a/block/vmdk.c b/block/vmdk.c
index 9a09193f3b..28cec50f38 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1263,7 +1263,6 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
     int ret;
     BDRVVmdkState *s = bs->opaque;
     uint32_t magic;
-    Error *local_err = NULL;
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
                                BDRV_CHILD_IMAGE, false, errp);
@@ -1317,9 +1316,8 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vmdk format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail;
     }
diff --git a/block/vpc.c b/block/vpc.c
index 36412f764d..7290f36514 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -448,9 +448,8 @@ static int vpc_open(BlockDriverState *bs, QDict *options, int flags,
     error_setg(&s->migration_blocker, "The vpc format used by node '%s' "
                "does not support live migration",
                bdrv_get_device_or_node_name(bs));
-    ret = migrate_add_blocker(s->migration_blocker, &local_err);
-    if (local_err) {
-        error_propagate(errp, local_err);
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
         error_free(s->migration_blocker);
         goto fail;
     }
diff --git a/block/vvfat.c b/block/vvfat.c
index c65a98e3ee..a28e3fa442 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1282,9 +1282,8 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
                    "The vvfat (rw) format used by node '%s' "
                    "does not support live migration",
                    bdrv_get_device_or_node_name(bs));
-        ret = migrate_add_blocker(s->migration_blocker, &local_err);
-        if (local_err) {
-            error_propagate(errp, local_err);
+        ret = migrate_add_blocker(s->migration_blocker, errp);
+        if (ret < 0) {
             error_free(s->migration_blocker);
             goto fail;
         }
diff --git a/hw/display/virtio-gpu-base.c b/hw/display/virtio-gpu-base.c
index c159351be3..7961308606 100644
--- a/hw/display/virtio-gpu-base.c
+++ b/hw/display/virtio-gpu-base.c
@@ -128,7 +128,6 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(qdev);
     VirtIOGPUBase *g = VIRTIO_GPU_BASE(qdev);
-    Error *local_err = NULL;
     int i;
 
     if (g->conf.max_outputs > VIRTIO_GPU_MAX_SCANOUTS) {
@@ -139,9 +138,7 @@ virtio_gpu_base_device_realize(DeviceState *qdev,
     g->use_virgl_renderer = false;
     if (virtio_gpu_virgl_enabled(g->conf)) {
         error_setg(&g->migration_blocker, "virgl is not yet migratable");
-        migrate_add_blocker(g->migration_blocker, &local_err);
-        if (local_err) {
-            error_propagate(errp, local_err);
+        if (migrate_add_blocker(g->migration_blocker, errp) < 0) {
             error_free(g->migration_blocker);
             return false;
         }
diff --git a/hw/intc/arm_gic_kvm.c b/hw/intc/arm_gic_kvm.c
index d7df423a7a..07b95143c9 100644
--- a/hw/intc/arm_gic_kvm.c
+++ b/hw/intc/arm_gic_kvm.c
@@ -517,9 +517,7 @@ static void kvm_arm_gic_realize(DeviceState *dev, Error **errp)
     if (!kvm_arm_gic_can_save_restore(s)) {
         error_setg(&s->migration_blocker, "This operating system kernel does "
                                           "not support vGICv2 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;
         }
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)
         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;
         }
diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
index ca43bf87ca..eddd07c743 100644
--- a/hw/intc/arm_gicv3_kvm.c
+++ b/hw/intc/arm_gicv3_kvm.c
@@ -858,9 +858,7 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error **errp)
                                GICD_CTLR)) {
         error_setg(&s->migration_blocker, "This operating system kernel does "
                                           "not support vGICv3 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;
         }
diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
index a8dc9b377d..fc128b25e2 100644
--- a/hw/misc/ivshmem.c
+++ b/hw/misc/ivshmem.c
@@ -898,9 +898,7 @@ static void ivshmem_common_realize(PCIDevice *dev, Error **errp)
     if (!ivshmem_is_master(s)) {
         error_setg(&s->migration_blocker,
                    "Migration is disabled when using feature 'peer mode' in device 'ivshmem'");
-        migrate_add_blocker(s->migration_blocker, &err);
-        if (err) {
-            error_propagate(errp, err);
+        if (migrate_add_blocker(s->migration_blocker, errp) < 0) {
             error_free(s->migration_blocker);
             return;
         }
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index c1b012aea4..13b05af29b 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -207,9 +207,7 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
                 "When external environment supports it (Orchestrator migrates "
                 "target SCSI device state or use shared storage over network), "
                 "set 'migratable' property to true to enable migration.");
-        migrate_add_blocker(vsc->migration_blocker, &err);
-        if (err) {
-            error_propagate(errp, err);
+        if (migrate_add_blocker(vsc->migration_blocker, errp) < 0) {
             error_free(vsc->migration_blocker);
             goto free_virtio;
         }
-- 
2.26.2