From ae0f57f0aa03571045a3accc0b22d91a4775e63c Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 8 Nov 2019 09:36:35 +0100 Subject: block: Remove 'backing': null from bs->{explicit_,}options bs->options and bs->explicit_options shouldn't contain any options for child nodes. bdrv_open_inherited() takes care to remove any options that match a child name after opening the image and the same is done when reopening. However, we miss the case of 'backing': null, which is a child option, but results in no child being created. This means that a 'backing': null remains in bs->options and bs->explicit_options. A typical use for 'backing': null is in live snapshots: blockdev-add for the qcow2 overlay makes sure not to open the backing file (because it is already opened and blockdev-snapshot will attach it). After doing a blockdev-snapshot, bs->options and bs->explicit_options become inconsistent with the actual state (bs has a backing file now, but the options still say null). On the next occasion that the image is reopened, e.g. switching it from read-write to read-only when another snapshot is taken, the option will take effect again and the node incorrectly loses its backing file. Fix bdrv_open_inherited() to remove the 'backing' option from bs->options and bs->explicit_options even for the case where it specifies that no backing file is wanted. Reported-by: Peter Krempa Signed-off-by: Kevin Wolf Reviewed-by: Alberto Garcia Tested-by: Peter Krempa --- block.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/block.c b/block.c index 4cffc2b..473eb6e 100644 --- a/block.c +++ b/block.c @@ -3019,6 +3019,8 @@ static BlockDriverState *bdrv_open_inherit(const char *filename, "use \"backing\": null instead"); } flags |= BDRV_O_NO_BACKING; + qdict_del(bs->explicit_options, "backing"); + qdict_del(bs->options, "backing"); qdict_del(options, "backing"); } -- cgit v1.1