From a13de40a05478e64726dd9861135d344837f3c30 Mon Sep 17 00:00:00 2001 From: Vladimir Sementsov-Ogievskiy Date: Sat, 11 Sep 2021 15:00:27 +0300 Subject: [PATCH] block: bdrv_inactivate_recurse(): check for permissions and fix crash We must not inactivate child when parent has write permissions on it. Calling .bdrv_inactivate() doesn't help: actually only qcow2 has this handler and it is used to flush caches, not for permission manipulations. So, let's simply check cumulative parent permissions before inactivating the node. This commit fixes a crash when we do migration during backup: prior to the commit nothing prevents all nodes inactivation at migration finish and following backup write to the target crashes on assertion "assert(!(bs->open_flags & BDRV_O_INACTIVE));" in bdrv_co_write_req_prepare(). After the commit, we rely on the fact that copy-before-write filter keeps write permission on target node to be able to write to it. So inactivation fails and migration fails as expected. Corresponding test now passes, so, enable it. Signed-off-by: Vladimir Sementsov-Ogievskiy Reviewed-by: Hanna Reitz Message-Id: <20210911120027.8063-3-vsementsov@virtuozzo.com> Signed-off-by: Hanna Reitz --- block.c | 8 ++++++++ tests/qemu-iotests/tests/migrate-during-backup | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index 00982edf45..5ce08a79fd 100644 --- a/block.c +++ b/block.c @@ -6326,6 +6326,7 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs) { BdrvChild *child, *parent; int ret; + uint64_t cumulative_perms, cumulative_shared_perms; if (!bs->drv) { return -ENOMEDIUM; @@ -6356,6 +6357,13 @@ static int bdrv_inactivate_recurse(BlockDriverState *bs) } } + bdrv_get_cumulative_perm(bs, &cumulative_perms, + &cumulative_shared_perms); + if (cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) { + /* Our inactive parents still need write access. Inactivation failed. */ + return -EPERM; + } + bs->open_flags |= BDRV_O_INACTIVE; /* diff --git a/tests/qemu-iotests/tests/migrate-during-backup b/tests/qemu-iotests/tests/migrate-during-backup index 1046904c5a..34103229ee 100755 --- a/tests/qemu-iotests/tests/migrate-during-backup +++ b/tests/qemu-iotests/tests/migrate-during-backup @@ -1,5 +1,5 @@ #!/usr/bin/env python3 -# group: migration disabled +# group: migration # # Copyright (c) 2021 Virtuozzo International GmbH #