Описание
In the Linux kernel, the following vulnerability has been resolved:
pNFS: Fix uninited ptr deref in block/scsi layout
The error occurs on the third attempt to encode extents. When function
ext_tree_prepare_commit() reallocates a larger buffer to retry encoding
extents, the "layoutupdate_pages" page array is initialized only after the
retry loop. But ext_tree_free_commitdata() is called on every iteration
and tries to put pages in the array, thus dereferencing uninitialized
pointers.
An additional problem is that there is no limit on the maximum possible
buffer_size. When there are too many extents, the client may create a
layoutcommit that is larger than the maximum possible RPC size accepted
by the server.
During testing, we observed two typical scenarios. First, one memory page
for extents is enough when we work with small files, append data to the
end of the file, or preallocate extents before writing. But when we fill
a new large file without preallocating, the number of extents can be huge,
and counting the number of written extents in ext_tree_encode_commit()
does not help much. Since this number increases even more between
unlocking and locking of ext_tree, the reallocated buffer may not be
large enough again and again.
A null pointer dereference flaw in the Linux kernel pNFS driver was found in the way extent encoding retry logic handles its page array.
A local user being NFS client can trigger this condition and cause this client machine to crash, resulting in a denial of service. The same path can also allow a layout commit to grow without an upper bound, which may reproduce RPC payloads larger than the server accepts (and server just ignores such requests, so still the problems only for client itself).
Отчет
A bug in the pNFS block/SCSI client path allowed ext_tree_free_commitdata() to dereference entries of layoutupdate_pages before that array was initialized during repeated extent-encoding retries, causing a kernel crash on the NFS client. In addition, the buffer size could grow without a proper cap, risking over-large layoutcommit RPCs.
Меры по смягчению последствий
To mitigate this issue, prevent the blockoutlayoutdriver module from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Fix deferred |
Показывать по
Дополнительная информация
Статус:
EPSS
6.2 Medium
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extents...
In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extent
In the Linux kernel, the following vulnerability has been resolved: p ...
In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of ext...
EPSS
6.2 Medium
CVSS3