Описание
A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size. A local attacker could use this flaw to leak data on the XFS filesystem otherwise not accessible to them.
Меры по смягчению последствий
This issue can be mitigated by ensuring xfs_alloc_file_space is not called with "0" as an argument. This can be done with a SystemTap script (which resets "0" with XFS_BMAPI_PREALLOC), below are the steps:
- Save the following script in a 'CVE-2021-4155.stp' file --- On Red Hat Enterprise Linux 6 --- probe module("xfs").function("xfs_alloc_file_space") { if ($alloc_type == 0) $alloc_type = 0x40;# XFS_BMAPI_PREALLOC } --- On Red Hat Enterprise Linux 6 --- --- On Red Hat Enterprise Linux 7 onwards --- probe module("xfs").function("xfs_alloc_file_space") { if ($alloc_type == 0) $alloc_type = 0x8;# XFS_BMAPI_PREALLOC } --- On Red Hat Enterprise Linux 7 onwards ---
- Install systemtap package and its dependencies
yum install -y systemtap systemtap-runtime
yum install -y kernel-devel kernel-debuginfo
- Build the mitigation kernel module as root.
stap -r uname -r -m cve_2021_4155.ko -g CVE-2021-4155.stp -p4
- Load the mitigation module as root
staprun -L cve_2021_4155.ko
What is SystemTap and how to use it? https://access.redhat.com/solutions/5441
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 5 | kernel | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Not affected | ||
| Red Hat Enterprise Linux 6 Extended Lifecycle Support | kernel | Fixed | RHSA-2022:1417 | 19.04.2022 |
| Red Hat Enterprise Linux 7 | kernel-rt | Fixed | RHSA-2022:0622 | 22.02.2022 |
| Red Hat Enterprise Linux 7 | kpatch-patch | Fixed | RHSA-2022:0592 | 22.02.2022 |
| Red Hat Enterprise Linux 7 | kernel | Fixed | RHSA-2022:0620 | 22.02.2022 |
| Red Hat Enterprise Linux 7.3 Advanced Update Support | kernel | Fixed | RHSA-2022:0529 | 15.02.2022 |
| Red Hat Enterprise Linux 7.4 Advanced Update Support | kernel | Fixed | RHSA-2022:0530 | 15.02.2022 |
| Red Hat Enterprise Linux 7.6 Advanced Update Support(Disable again in 2026 - SPRHEL-7118) | kernel | Fixed | RHSA-2022:0531 | 15.02.2022 |
| Red Hat Enterprise Linux 7.6 Telco Extended Update Support | kernel | Fixed | RHSA-2022:0531 | 15.02.2022 |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size. A local attacker could use this flaw to leak data on the XFS filesystem otherwise not accessible to them.
A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS filesystem allowed for size increase of files with unaligned size. A local attacker could use this flaw to leak data on the XFS filesystem otherwise not accessible to them.
A data leak flaw was found in the way XFS_IOC_ALLOCSP IOCTL in the XFS ...
Уязвимость реализации системных вызовов ioctl(XFS_IOC_ALLOCSP) и ioctl(XFS_IOC_FREESP) файловой системы XFS ядра операционных систем Linux, позволяющая нарушителю получить несанкционированный доступ к защищаемой информации
EPSS
5.5 Medium
CVSS3