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[PATCH 2/3] backup-top: Refuse I/O in inactive state
From: |
Max Reitz |
Subject: |
[PATCH 2/3] backup-top: Refuse I/O in inactive state |
Date: |
Fri, 19 Feb 2021 16:33:47 +0100 |
When the backup-top node transitions from active to inactive in
bdrv_backup_top_drop(), the BlockCopyState is freed and the filtered
child is removed, so the node effectively becomes unusable.
However, noone told its I/O functions this, so they will happily
continue accessing bs->backing and s->bcs. Prevent that by aborting
early when s->active is false.
(After the preceding patch, the node should be gone after
bdrv_backup_top_drop(), so this should largely be a theoretical problem.
But still, better to be safe than sorry, and also I think it just makes
sense to check s->active in the I/O functions.)
Signed-off-by: Max Reitz <mreitz@redhat.com>
---
block/backup-top.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/block/backup-top.c b/block/backup-top.c
index d1253e1aa6..589e8b651d 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -45,6 +45,12 @@ static coroutine_fn int backup_top_co_preadv(
BlockDriverState *bs, uint64_t offset, uint64_t bytes,
QEMUIOVector *qiov, int flags)
{
+ BDRVBackupTopState *s = bs->opaque;
+
+ if (!s->active) {
+ return -EIO;
+ }
+
return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
}
@@ -54,6 +60,10 @@ static coroutine_fn int backup_top_cbw(BlockDriverState *bs,
uint64_t offset,
BDRVBackupTopState *s = bs->opaque;
uint64_t off, end;
+ if (!s->active) {
+ return -EIO;
+ }
+
if (flags & BDRV_REQ_WRITE_UNCHANGED) {
return 0;
}
--
2.29.2