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Several deficiencies in the libblockdev utils/exec code were found upstream, potentially leading to deadlock or an infinite loop. Tests demonstrating the issues are available.
Fixed upstream: https://github.com/storaged-project/libblockdev/pull/572
Steps to reproduce:
1. create and activate 400 or more LVM snapshots
2. start udisksd, observe infinite loop
Since UDisks and possibly other tools use this libblockdev functionality, it's only a matter of time until this issue demonstrates on the client side.
Comment 3guazhang@redhat.com
2020-11-23 07:44:22 UTC
Hi,
I can not reproduce the bug with libblockdev-2.24-2.el8, Could you please provides more details.
test steps:
pvcreate /dev/sdb
vgcreate myvol /dev/sdb
lvcreate -L 200G -n date myvol
mkfs.xfs /dev/myvol/date
mkdir -p test
mount /dev/myvol/date test
for i in {1..400};do
touch test/txt$i
lvcreate -L 10M -p r -s -n datesnap$i /dev/myvol/date
done
systemctl restart udisks2
UDisks should still work but you should see stuck lvm processes and UDisks threads waiting for output on the system. I'm changing the needinfo to Tomáš, he might provide a more detailed reproducer.
Btw. we also added a good regression test for this bug, so it might be enough to check that "test_exec_buffer_bloat" passed in the gating.
You need to have the `lvm2` module activated in UDisks. Use
> gdbus call -y -d org.freedesktop.UDisks2 -o /org/freedesktop/UDisks2/Manager -m org.freedesktop.UDisks2.Manager.EnableModule -- lvm2 true
to enable it.
Then you can use either your reproducer or find inspiration in my loadtests: https://github.com/storaged-project/udisks/pull/814
Please note the issue is not lvm2-specific and certain tools may trigger that as well (we've had reports about dumpe2fs calls AFAIR).
Comment 6guazhang@redhat.com
2020-11-30 01:41:45 UTC
Thanks for the guide.
Don't hit the bug with fixed package, move to verified.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory (libblockdev bug fix and enhancement update), and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2021:1820