From: Max Reitz <mreitz@redhat.com>
To: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Alberto Garcia <berto@igalia.com>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>
Subject: [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK
Date: Mon, 28 Oct 2019 17:18:39 +0100 [thread overview]
Message-ID: <20191028161841.1198-1-mreitz@redhat.com> (raw)
This fixes a bug reported on
https://bugs.launchpad.net/qemu/+bug/1850000. The problem is that
QCOW2_COMPRESSED_SECTOR_MASK is a 32-bit mask when it really needs to be
a 64-bit mask.
The launchpad report mentions only problems with qemu-img check on large
compressed images, but I think it might extend further than that:
- I suppose qcow2_free_any_clusters() would free every compressed offset
modulo 4G, which isn’t good
- qcow2_update_snapshot_refcount() will probably update compressed
cluster’s refcounts (in snapshots) modulo 4G, which also isn’t good
- And then we have check_refcount_l2() which updates the wrong clusters
for qemu-img check (as demonstrated in the bug report)
- (qcow2_co_preadv_compressed() is safe because it uses the inverted
mask, which of course is again just 32 bit)
But I haven’t tested those other cases.
Max Reitz (2):
qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK
iotests: Add test for 4G+ compressed qcow2 write
block/qcow2.h | 2 +-
tests/qemu-iotests/272 | 79 ++++++++++++++++++++++++++++++++++++++
tests/qemu-iotests/272.out | 10 +++++
tests/qemu-iotests/group | 1 +
4 files changed, 91 insertions(+), 1 deletion(-)
create mode 100755 tests/qemu-iotests/272
create mode 100644 tests/qemu-iotests/272.out
--
2.21.0
next reply other threads:[~2019-10-28 17:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 16:18 Max Reitz [this message]
2019-10-28 16:18 ` [PATCH for-4.2 1/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK Max Reitz
2019-10-28 16:18 ` [PATCH for-4.2 2/2] iotests: Add test for 4G+ compressed qcow2 write Max Reitz
2019-10-28 22:36 ` [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK Alberto Garcia
2019-11-06 11:19 ` Max Reitz
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