stream: fix crash in stream_start() when block_job_create() fails

[mirror_qemu.git] / block / stream.c

diff --git a/block/stream.c b/block/stream.c
index b05856bd65492819055c55f28c6741580751c17a..52d329f5c62552c5b71da6a8abf28340172964ac 100644 (file)
--- a/block/stream.c
+++ b/block/stream.c
@@ -68,6 +68,7 @@ static void stream_complete(BlockJob *job, void *opaque)
     StreamCompleteData *data = opaque;
     BlockDriverState *bs = blk_bs(job->blk);
     BlockDriverState *base = s->base;
+    Error *local_err = NULL;
 
     if (!block_job_is_cancelled(&s->common) && data->reached_end &&
         data->ret == 0) {
@@ -79,11 +80,19 @@ static void stream_complete(BlockJob *job, void *opaque)
             }
         }
         data->ret = bdrv_change_backing_file(bs, base_id, base_fmt);
-        bdrv_set_backing_hd(bs, base);
+        bdrv_set_backing_hd(bs, base, &local_err);
+        if (local_err) {
+            error_report_err(local_err);
+            data->ret = -EPERM;
+            goto out;
+        }
     }
 
+out:
     /* Reopen the image back in read-only mode if necessary */
     if (s->bs_flags != bdrv_get_flags(bs)) {
+        /* Give up write permissions before making it read-only */
+        blk_set_perm(job->blk, 0, BLK_PERM_ALL, &error_abort);
         bdrv_reopen(bs, s->bs_flags, NULL);
     }
 
@@ -218,6 +227,7 @@ static const BlockJobDriver stream_job_driver = {
     .instance_size = sizeof(StreamBlockJob),
     .job_type      = BLOCK_JOB_TYPE_STREAM,
     .set_speed     = stream_set_speed,
+    .start         = stream_run,
 };
 
 void stream_start(const char *job_id, BlockDriverState *bs,
@@ -228,25 +238,35 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     BlockDriverState *iter;
     int orig_bs_flags;
 
-    s = block_job_create(job_id, &stream_job_driver, bs, speed,
-                         BLOCK_JOB_DEFAULT, NULL, NULL, errp);
-    if (!s) {
-        return;
-    }
-
     /* Make sure that the image is opened in read-write mode */
     orig_bs_flags = bdrv_get_flags(bs);
     if (!(orig_bs_flags & BDRV_O_RDWR)) {
         if (bdrv_reopen(bs, orig_bs_flags | BDRV_O_RDWR, errp) != 0) {
-            block_job_unref(&s->common);
             return;
         }
     }
 
-    /* Block all intermediate nodes between bs and base, because they
-     * will disappear from the chain after this operation */
+    /* Prevent concurrent jobs trying to modify the graph structure here, we
+     * already have our own plans. Also don't allow resize as the image size is
+     * queried only at the job start and then cached. */
+    s = block_job_create(job_id, &stream_job_driver, bs,
+                         BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
+                         BLK_PERM_GRAPH_MOD,
+                         BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED |
+                         BLK_PERM_WRITE,
+                         speed, BLOCK_JOB_DEFAULT, NULL, NULL, errp);
+    if (!s) {
+        goto fail;
+    }
+
+    /* Block all intermediate nodes between bs and base, because they will
+     * disappear from the chain after this operation. The streaming job reads
+     * every block only once, assuming that it doesn't change, so block writes
+     * and resizes. */
     for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
-        block_job_add_bdrv(&s->common, iter);
+        block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
+                           BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED,
+                           &error_abort);
     }
 
     s->base = base;
@@ -254,7 +274,12 @@ void stream_start(const char *job_id, BlockDriverState *bs,
     s->bs_flags = orig_bs_flags;
 
     s->on_error = on_error;
-    s->common.co = qemu_coroutine_create(stream_run, s);
-    trace_stream_start(bs, base, s, s->common.co);
-    qemu_coroutine_enter(s->common.co);
+    trace_stream_start(bs, base, s);
+    block_job_start(&s->common);
+    return;
+
+fail:
+    if (orig_bs_flags != bdrv_get_flags(bs)) {
+        bdrv_reopen(bs, orig_bs_flags, NULL);
+    }
 }