[Qemu-devel] [PATCH v2] blockjob: update nodes head while removing all bdrv

[Sergio Lopez]

block_job_remove_all_bdrv() iterates through job->nodes, calling
bdrv_root_unref_child() for each entry. The call to the latter may
reach child_job_[can_]set_aio_ctx(), which will also attempt to
traverse job->nodes, potentially finding entries that where freed
on previous iterations.

To avoid this situation, update job->nodes head on each iteration to
ensure that already freed entries are no longer linked to the list.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=1746631
Signed-off-by: Sergio Lopez <address@hidden>
---
Changelog

v2:
 - Avoid leaking job->nodes (thanks Max Reitz)
---
 blockjob.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/blockjob.c b/blockjob.c
index 6e32d1a0c0..ffda6dd1e4 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -187,13 +187,21 @@ static const BdrvChildRole child_job = {
 
 void block_job_remove_all_bdrv(BlockJob *job)
 {
-    GSList *l;
+    GSList *l, *orig_nodes;
+
+    orig_nodes = job->nodes;
     for (l = job->nodes; l; l = l->next) {
         BdrvChild *c = l->data;
         bdrv_op_unblock_all(c->bs, job->blocker);
         bdrv_root_unref_child(c);
+        /*
+         * The call above may reach child_job_[can_]set_aio_ctx(), which will
+         * also traverse job->nodes, so update the head here to make sure it
+         * doesn't attempt to process an already freed BdrvChild.
+         */
+        job->nodes = l->next;
     }
-    g_slist_free(job->nodes);
+    g_slist_free(orig_nodes);
     job->nodes = NULL;
 }
 
-- 
2.21.0