Описание
In the Linux kernel, the following vulnerability has been resolved:
vhost: reset the vring metadata cache on vring reconfiguration
vq->meta_iotlb[] caches the vhost_iotlb_map that backs each vring
metadata region, and iotlb_access_ok() returns early on a cache hit,
taking the hit as proof that the region has already been validated:
if (vhost_vq_meta_fetch(vq, addr, len, type))
return true;
The cache is reset on VHOST_IOTLB_UPDATE and VHOST_IOTLB_INVALIDATE, on
device IOTLB (re)initialisation and on vq reset, but not when
VHOST_SET_VRING_ADDR replaces vq->desc, vq->avail and vq->used, nor when
VHOST_SET_VRING_NUM changes the region sizes.
With a device IOTLB attached both ioctls are accepted while the vq is
live, and neither validates the addresses at ioctl time: vq_access_ok()
and vq_log_used_access_ok() return true early because the addresses are
GIOVAs, deferring validation to prefetch time. Once the cache has been
populated that deferred validation no longer runs -- vq_meta_prefetch()
hits the stale entry and returns true -- and vhost_vq_meta_fetch() keeps
translating through the old mapping as
map->addr + addr - map->start
for an address the mapping no longer covers. vhost_copy_to_user() and
vhost_copy_from_user() consume the result with __copy_to_user() and
__copy_from_user(), which do not check it either, so a subsequent used
ring update or descriptor fetch accesses memory outside the region the
IOTLB actually maps.
Reset the metadata cache whenever the vring is reconfigured, so the new
addresses are pushed back through iotlb_access_ok()'s slow path.
A flaw was found in the Linux kernel's vhost subsystem. A local attacker could exploit this vulnerability by reconfiguring a virtual ring (vring) using specific ioctl commands while a device Input/Output Memory Management Unit (IOTLB) is attached. This improper handling of the vring metadata cache can lead to out-of-bounds memory access, potentially resulting in information disclosure, data corruption, or a denial of service.
Меры по смягчению последствий
Prevent the vhost kernel module from loading on systems where kernel-accelerated virtio is not required.
- Add a configuration entry in /etc/modprobe.d to disable autoloading:
echo "install vhost /bin/true" > /etc/modprobe.d/disable-vhost.conf
- If the module is already loaded and no guests are using it, unload the vhost drivers:
modprobe -r vhost_net vhost_vsock vhost_scsi vhost
Caveats: Disabling vhost prevents in-kernel acceleration for virtio networking, storage, and vsock communication, which may degrade I/O performance or cause virtual machine instances dependent on vhost devices to fail to start. Warning: A system reboot or stopping active virtual machines is required if the driver is currently loaded and actively in use.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 6 | kernel | Affected | ||
| Red Hat Enterprise Linux 10 | kernel | Fixed | RHSA-2026:57251 | 20.08.2026 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | kernel | Fixed | RHSA-2026:61351 | 31.08.2026 |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | kernel-rt | Fixed | RHSA-2026:81371 | 12.10.2026 |
| Red Hat Enterprise Linux 7 Extended Lifecycle Support | kernel | Fixed | RHSA-2026:81349 | 12.10.2026 |
| Red Hat Enterprise Linux 8 | kernel-rt | Fixed | RHSA-2026:55765 | 17.08.2026 |
| Red Hat Enterprise Linux 8 | kernel | Fixed | RHSA-2026:55764 | 17.08.2026 |
| Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | kernel | Fixed | RHSA-2026:65710 | 09.09.2026 |
| Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | kernel | Fixed | RHSA-2026:65710 | 09.09.2026 |
| Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | kernel | Fixed | RHSA-2026:59473 | 25.08.2026 |
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Дополнительная информация
Статус:
8.7 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: vhost: reset the vring metadata cache on vring reconfiguration vq->meta_iotlb[] caches the vhost_iotlb_map that backs each vring metadata region, and iotlb_access_ok() returns early on a cache hit, taking the hit as proof that the region has already been validated: if (vhost_vq_meta_fetch(vq, addr, len, type)) return true; The cache is reset on VHOST_IOTLB_UPDATE and VHOST_IOTLB_INVALIDATE, on device IOTLB (re)initialisation and on vq reset, but not when VHOST_SET_VRING_ADDR replaces vq->desc, vq->avail and vq->used, nor when VHOST_SET_VRING_NUM changes the region sizes. With a device IOTLB attached both ioctls are accepted while the vq is live, and neither validates the addresses at ioctl time: vq_access_ok() and vq_log_used_access_ok() return true early because the addresses are GIOVAs, deferring validation to prefetch time. Once the cache has been populated that deferred validation no longer runs -- vq_meta_pref...
In the Linux kernel, the following vulnerability has been resolved: vhost: reset the vring metadata cache on vring reconfiguration vq->meta_iotlb[] caches the vhost_iotlb_map that backs each vring metadata region, and iotlb_access_ok() returns early on a cache hit, taking the hit as proof that the region has already been validated: if (vhost_vq_meta_fetch(vq, addr, len, type)) return true; The cache is reset on VHOST_IOTLB_UPDATE and VHOST_IOTLB_INVALIDATE, on device IOTLB (re)initialisation and on vq reset, but not when VHOST_SET_VRING_ADDR replaces vq->desc, vq->avail and vq->used, nor when VHOST_SET_VRING_NUM changes the region sizes. With a device IOTLB attached both ioctls are accepted while the vq is live, and neither validates the addresses at ioctl time: vq_access_ok() and vq_log_used_access_ok() return true early because the addresses are GIOVAs, deferring validation to prefetch time. Once the cache has been populated that deferred validation no longer runs -- vq_meta
vhost: reset the vring metadata cache on vring reconfiguration
In the Linux kernel, the following vulnerability has been resolved: v ...
In the Linux kernel, the following vulnerability has been resolved: vhost: reset the vring metadata cache on vring reconfiguration vq->meta_iotlb[] caches the vhost_iotlb_map that backs each vring metadata region, and iotlb_access_ok() returns early on a cache hit, taking the hit as proof that the region has already been validated: if (vhost_vq_meta_fetch(vq, addr, len, type)) return true; The cache is reset on VHOST_IOTLB_UPDATE and VHOST_IOTLB_INVALIDATE, on device IOTLB (re)initialisation and on vq reset, but not when VHOST_SET_VRING_ADDR replaces vq->desc, vq->avail and vq->used, nor when VHOST_SET_VRING_NUM changes the region sizes. With a device IOTLB attached both ioctls are accepted while the vq is live, and neither validates the addresses at ioctl time: vq_access_ok() and vq_log_used_access_ok() return true early because the addresses are GIOVAs, deferring validation to prefetch time. Once the cache has been populated that deferred validation no longer runs -- vq_m...
8.7 High
CVSS3