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[Qemu-devel] [PATCH v3] blockjob: update nodes head while removing all b
From: |
Max Reitz |
Subject: |
[Qemu-devel] [PATCH v3] blockjob: update nodes head while removing all bdrv |
Date: |
Wed, 11 Sep 2019 12:03:16 +0200 |
From: Sergio Lopez <address@hidden>
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>
Cc: address@hidden
Signed-off-by: Max Reitz <address@hidden>
---
v3:
- Rewrote the loop to make the whole function a bit simpler
(Also, remove the node from the job->nodes list before unref'ing it,
just to be extra-safe)
---
blockjob.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/blockjob.c b/blockjob.c
index 2abed0f551..c6e20e2fcd 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -175,14 +175,23 @@ 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)
--
2.21.0
- [Qemu-devel] [PATCH v3] blockjob: update nodes head while removing all bdrv,
Max Reitz <=