error: Avoid error_propagate() after migrate_add_blocker()

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>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200707160613.848843-43-armbru@redhat.com>

7 files changed, 14 insertions, 25 deletions

diff --git a/block/parallels.c b/block/parallels.c
index f489c0d4ba..3c22dfdc9d 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -859,9 +859,8 @@ 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 c22d1bf6b8..1e134f3445 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 2496d51a4d..5627e7d764 100644
--- a/block/vdi.c
+++ b/block/vdi.c
@@ -374,7 +374,6 @@ 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,
@@ -495,9 +494,8 @@ 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 a36d9d924a..791eb90263 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 131b9db6cc..890554277e 100644
--- a/block/vpc.c
+++ b/block/vpc.c
@@ -446,9 +446,8 @@ 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 24d36220d3..36b53c8757 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1141,7 +1141,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
     bool floppy;
     const char *dirname, *label;
     QemuOpts *opts;
-    Error *local_err = NULL;
     int ret;
 
 #ifdef DEBUG
@@ -1267,9 +1266,8 @@ 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;
         }