From: Sergio Lopez Date: Wed, 11 Sep 2019 12:03:16 +0200 Subject: blockjob: update nodes head while removing all bdrv Git-commit: d876bf676f5e7c6aa9ac64555e48cba8734ecb2f 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 Cc: qemu-stable@nongnu.org Signed-off-by: Max Reitz Message-id: 20190911100316.32282-1-mreitz@redhat.com Reviewed-by: Sergio Lopez Signed-off-by: Max Reitz Signed-off-by: Bruce Rogers --- blockjob.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/blockjob.c b/blockjob.c index 20b7f557da3e491927b99b113b73..74abb97bfdf27b5a9f4f82cd55b4 100644 --- a/blockjob.c +++ b/blockjob.c @@ -186,14 +186,23 @@ static const BdrvChildRole child_job = { void block_job_remove_all_bdrv(BlockJob *job) { - GSList *l; - for (l = job->nodes; l; l = l->next) { + /* + * bdrv_root_unref_child() may reach child_job_[can_]set_aio_ctx(), + * which will also traverse job->nodes, so consume the list one by + * one to make sure that such a concurrent access does not attempt + * to process an already freed BdrvChild. + */ + while (job->nodes) { + GSList *l = job->nodes; BdrvChild *c = l->data; + + job->nodes = l->next; + bdrv_op_unblock_all(c->bs, job->blocker); bdrv_root_unref_child(c); + + g_slist_free_1(l); } - g_slist_free(job->nodes); - job->nodes = NULL; } bool block_job_has_bdrv(BlockJob *job, BlockDriverState *bs)