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qemu/block-backend-Retain-permissions-after-m.patch
2022-05-27 12:52:53 +00:00

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From: Hanna Reitz <hreitz@redhat.com>
Date: Thu, 25 Nov 2021 14:53:16 +0100
Subject: block-backend: Retain permissions after migration
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Git-commit: 492a119610129f65217580790971fa038e5492d3
After migration, the permissions the guest device wants to impose on its
BlockBackend are stored in blk->perm and blk->shared_perm. In
blk_root_activate(), we take our permissions, but keep all shared
permissions open by calling `blk_set_perm(blk->perm, BLK_PERM_ALL)`.
Only afterwards (immediately or later, depending on the runstate) do we
restrict the shared permissions by calling
`blk_set_perm(blk->perm, blk->shared_perm)`. Unfortunately, our first
call with shared_perm=BLK_PERM_ALL has overwritten blk->shared_perm to
be BLK_PERM_ALL, so this is a no-op and the set of shared permissions is
not restricted.
Fix this bug by saving the set of shared permissions before invoking
blk_set_perm() with BLK_PERM_ALL and restoring it afterwards.
Fixes: 5f7772c4d0cf32f4e779fcd5a69ae4dae24aeebf
("block-backend: Defer shared_perm tightening migration
completion")
Reported-by: Peng Liang <liangpeng10@huawei.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20211125135317.186576-2-hreitz@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Peng Liang <liangpeng10@huawei.com>
Signed-off-by: Li Zhang <lizhang@suse.de>
---
block/block-backend.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/block/block-backend.c b/block/block-backend.c
index 12ef80ea170c04a15500b42bc5e7..41e388fe1f30af8f3cf6a872b37a 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -190,6 +190,7 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
{
BlockBackend *blk = child->opaque;
Error *local_err = NULL;
+ uint64_t saved_shared_perm;
if (!blk->disable_perm) {
return;
@@ -197,12 +198,22 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
blk->disable_perm = false;
+ /*
+ * blk->shared_perm contains the permissions we want to share once
+ * migration is really completely done. For now, we need to share
+ * all; but we also need to retain blk->shared_perm, which is
+ * overwritten by a successful blk_set_perm() call. Save it and
+ * restore it below.
+ */
+ saved_shared_perm = blk->shared_perm;
+
blk_set_perm(blk, blk->perm, BLK_PERM_ALL, &local_err);
if (local_err) {
error_propagate(errp, local_err);
blk->disable_perm = true;
return;
}
+ blk->shared_perm = saved_shared_perm;
if (runstate_check(RUN_STATE_INMIGRATE)) {
/* Activation can happen when migration process is still active, for