From 7ec94ee16262eb0da7fb7788347a65162845b1c2 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Wed, 10 Oct 2018 13:19:57 +0100 Subject: [PATCH 3/5] mirror: Fail gracefully for source == target RH-Author: Kevin Wolf Message-id: <20181010131957.23198-2-kwolf@redhat.com> Patchwork-id: 82564 O-Subject: [RHEL-8 qemu-kvm PATCH 1/1] mirror: Fail gracefully for source == target Bugzilla: 1637963 RH-Acked-by: John Snow RH-Acked-by: Fam Zheng RH-Acked-by: Stefan Hajnoczi blockdev-mirror with the same node for source and target segfaults today: A node is in its own backing chain, so mirror_start_job() decides that this is an active commit. When adding the intermediate nodes with block_job_add_bdrv(), it starts the iteration through the subchain with the backing file of source, though, so it never reaches target and instead runs into NULL at the base. While we could fix that by starting with source itself, there is no point in allowing mirroring a node into itself and I wouldn't be surprised if this caused more problems later. So just check for this scenario and error out. Cc: qemu-stable@nongnu.org Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake (cherry picked from commit 86fae10c64d642256cf019e6829929fa0d259c7a) Signed-off-by: Kevin Wolf Signed-off-by: Danilo C. L. de Paula --- block/mirror.c | 5 +++++ tests/qemu-iotests/041 | 6 ++++++ tests/qemu-iotests/041.out | 4 ++-- 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index 163b1d4..313e6e9 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -1149,6 +1149,11 @@ static void mirror_start_job(const char *job_id, BlockDriverState *bs, buf_size = DEFAULT_MIRROR_BUF_SIZE; } + if (bs == target) { + error_setg(errp, "Can't mirror node into itself"); + return; + } + /* In the case of active commit, add dummy driver to provide consistent * reads on the top, while disabling it in the intermediate nodes, and make * the backing chain writable. */ diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041 index c20ac7d..9336ab6 100755 --- a/tests/qemu-iotests/041 +++ b/tests/qemu-iotests/041 @@ -234,6 +234,12 @@ class TestSingleBlockdev(TestSingleDrive): result = self.vm.qmp("blockdev-add", **args) self.assert_qmp(result, 'return', {}) + def test_mirror_to_self(self): + result = self.vm.qmp(self.qmp_cmd, job_id='job0', + device=self.qmp_target, sync='full', + target=self.qmp_target) + self.assert_qmp(result, 'error/class', 'GenericError') + test_large_cluster = None test_image_not_found = None test_small_buffer2 = None diff --git a/tests/qemu-iotests/041.out b/tests/qemu-iotests/041.out index c28b392..e071d0b 100644 --- a/tests/qemu-iotests/041.out +++ b/tests/qemu-iotests/041.out @@ -1,5 +1,5 @@ -..................................................................................... +........................................................................................ ---------------------------------------------------------------------- -Ran 85 tests +Ran 88 tests OK -- 1.8.3.1