Описание
In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix zero size inode with non-zero size after log replay
When logging that an inode exists, as part of logging a new name or
logging new dir entries for a directory, we always set the generation of
the logged inode item to 0. This is to signal during log replay (in
overwrite_item()), that we should not set the i_size since we only logged
that an inode exists, so the i_size of the inode in the subvolume tree
must be preserved (as when we log new names or that an inode exists, we
don't log extents).
This works fine except when we have already logged an inode in full mode
or it's the first time we are logging an inode created in a past
transaction, that inode has a new i_size of 0 and then we log a new name
for the inode (due to a new hardlink or a rename), in which case we log
an i_size of 0 for the inode and a generation of 0, which causes the log
replay code to not update the inode's i_size to 0 (in overwrite_item()).
An example scenario:
mkdir /mnt/dir
xfs_io -f -c "pwrite 0 64K" /mnt/dir/foo
sync
xfs_io -c "truncate 0" -c "fsync" /mnt/dir/foo
ln /mnt/dir/foo /mnt/dir/bar
xfs_io -c "fsync" /mnt/dir
After log replay the file remains with a size of 64K. This is because when
we first log the inode, when we fsync file foo, we log its current i_size
of 0, and then when we create a hard link we log again the inode in exists
mode (LOG_INODE_EXISTS) but we set a generation of 0 for the inode item we
add to the log tree, so during log replay overwrite_item() sees that the
generation is 0 and i_size is 0 so we skip updating the inode's i_size
from 64K to 0.
Fix this by making sure at fill_inode_item() we always log the real
generation of the inode if it was logged in the current transaction with
the i_size we logged before. Also if an inode created in a previous
transaction is logged in exists mode only, make sure we log the i_size
stored in the inode item located from the commit root, so that if we log
multiple times that the inode exists we get the correct i_size.
A test case for fstests will follow soon.
A flaw was found in the Linux kernel's Btrfs filesystem. When a file is truncated to zero size and then a hardlink is created, a power failure followed by log replay can cause the file to incorrectly retain its original size instead of being zero. This data integrity issue may lead to unexpected file content after system recovery.
Отчет
Red Hat acknowledges the upstream Linux kernel correction for «btrfs» as described in COMMENT_ZERO. Fixes are delivered through standard kernel errata for supported products. Operational exposure depends on whether this subsystem or driver is active in your configuration.
Меры по смягчению последствий
To mitigate this issue, prevent the btrfs module from being loaded. See https://access.redhat.com/solutions/41278 for instructions.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected |
Показывать по
Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix zero size inode with non-zero size after log replay When logging that an inode exists, as part of logging a new name or logging new dir entries for a directory, we always set the generation of the logged inode item to 0. This is to signal during log replay (in overwrite_item()), that we should not set the i_size since we only logged that an inode exists, so the i_size of the inode in the subvolume tree must be preserved (as when we log new names or that an inode exists, we don't log extents). This works fine except when we have already logged an inode in full mode or it's the first time we are logging an inode created in a past transaction, that inode has a new i_size of 0 and then we log a new name for the inode (due to a new hardlink or a rename), in which case we log an i_size of 0 for the inode and a generation of 0, which causes the log replay code to not update the inode's i_size to 0 (in overwrite_...
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix zero size inode with non-zero size after log replay When logging that an inode exists, as part of logging a new name or logging new dir entries for a directory, we always set the generation of the logged inode item to 0. This is to signal during log replay (in overwrite_item()), that we should not set the i_size since we only logged that an inode exists, so the i_size of the inode in the subvolume tree must be preserved (as when we log new names or that an inode exists, we don't log extents). This works fine except when we have already logged an inode in full mode or it's the first time we are logging an inode created in a past transaction, that inode has a new i_size of 0 and then we log a new name for the inode (due to a new hardlink or a rename), in which case we log an i_size of 0 for the inode and a generation of 0, which causes the log replay code to not update the inode's i_size to 0 (in overwrite_
In the Linux kernel, the following vulnerability has been resolved: b ...
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix zero size inode with non-zero size after log replay When logging that an inode exists, as part of logging a new name or logging new dir entries for a directory, we always set the generation of the logged inode item to 0. This is to signal during log replay (in overwrite_item()), that we should not set the i_size since we only logged that an inode exists, so the i_size of the inode in the subvolume tree must be preserved (as when we log new names or that an inode exists, we don't log extents). This works fine except when we have already logged an inode in full mode or it's the first time we are logging an inode created in a past transaction, that inode has a new i_size of 0 and then we log a new name for the inode (due to a new hardlink or a rename), in which case we log an i_size of 0 for the inode and a generation of 0, which causes the log replay code to not update the inode's i_size to 0 (in overwri...
EPSS
5.5 Medium
CVSS3