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Re: [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK
From: |
Max Reitz |
Subject: |
Re: [PATCH for-4.2 0/2] qcow2: Fix QCOW2_COMPRESSED_SECTOR_MASK |
Date: |
Wed, 6 Nov 2019 12:19:17 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 |
On 28.10.19 17:18, Max Reitz wrote:
> 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
Thanks for the review, applied to my block branch:
https://git.xanclic.moe/XanClic/qemu/commits/branch/block
Max
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