Описание
In the Linux kernel, the following vulnerability has been resolved:
vsock/virtio: fix zerocopy completion for multi-skb sends
When a large message is fragmented into multiple skbs, the zerocopy
uarg is only allocated and attached to the last skb in the loop.
Non-final skbs carry pinned user pages with no completion tracking,
so the kernel has no way to notify userspace when those pages are safe
to reuse. If the loop breaks early the uarg is never allocated at all,
leaking pinned pages with no completion notification.
Fix this by following the approach used by TCP: allocate the zerocopy
uarg (if not provided by the caller) before the send loop and attach
it to every skb via skb_zcopy_set(), which takes a reference per skb.
Each skb's completion properly decrements the refcount, and the
notification only fires after the last skb is freed.
On failure, if no data was sent, the uarg is cleanly aborted via
net_zcopy_put_abort().
This issue was initially discovered by sashiko while reviewing commit
1cb36e252211 ("vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting")
but was pre-existing.
A flaw was found in the Linux kernel's vsock/virtio component. This vulnerability occurs during zerocopy completion for large messages fragmented into multiple socket kernel buffers (skbs). An issue in how user arguments (uargs) are handled for these buffers can lead to pinned user pages not being properly tracked or released. This prevents the kernel from notifying userspace when these memory pages are safe to reuse, potentially leading to memory leaks or data corruption if pages are prematurely reallocated. This issue could lead to local privilege escalation.
Отчет
Red Hat Enterprise Linux 9.2 and earlier are not affected by this flaw. The vulnerable code was introduced by the upstream commit that added MSG_ZEROCOPY support to the virtio-vsock transport (581512a). This feature was not backported to RHEL 9.2 or earlier kernel versions, so the affected zerocopy transmit code path does not exist in those kernels.
Меры по смягчению последствий
The vulnerable code path is only reachable when using virtio-vsock with zerocopy transmit on virtual machines using the vhost-vsock or virtio-vsock transport. Systems that do not use VM socket communication (AF_VSOCK) are not affected. To prevent the vulnerable code path from being reached, the vhost_vsock kernel module can be unloaded and blacklisted if vsock functionality is not required:
Systems that rely on VM-to-host socket communication (e.g., QEMU guest agent communication) cannot use this mitigation and should prioritize applying the kernel fix.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Affected | ||
| Red Hat Enterprise Linux 6 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Affected | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Affected |
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Дополнительная информация
Статус:
EPSS
7.8 High
CVSS3
Связанные уязвимости
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix zerocopy completion for multi-skb sends When a large message is fragmented into multiple skbs, the zerocopy uarg is only allocated and attached to the last skb in the loop. Non-final skbs carry pinned user pages with no completion tracking, so the kernel has no way to notify userspace when those pages are safe to reuse. If the loop breaks early the uarg is never allocated at all, leaking pinned pages with no completion notification. Fix this by following the approach used by TCP: allocate the zerocopy uarg (if not provided by the caller) before the send loop and attach it to every skb via skb_zcopy_set(), which takes a reference per skb. Each skb's completion properly decrements the refcount, and the notification only fires after the last skb is freed. On failure, if no data was sent, the uarg is cleanly aborted via net_zcopy_put_abort(). This issue was initially discovered by sashiko while reviewi...
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix zerocopy completion for multi-skb sends When a large message is fragmented into multiple skbs, the zerocopy uarg is only allocated and attached to the last skb in the loop. Non-final skbs carry pinned user pages with no completion tracking, so the kernel has no way to notify userspace when those pages are safe to reuse. If the loop breaks early the uarg is never allocated at all, leaking pinned pages with no completion notification. Fix this by following the approach used by TCP: allocate the zerocopy uarg (if not provided by the caller) before the send loop and attach it to every skb via skb_zcopy_set(), which takes a reference per skb. Each skb's completion properly decrements the refcount, and the notification only fires after the last skb is freed. On failure, if no data was sent, the uarg is cleanly aborted via net_zcopy_put_abort(). This issue was initially discovered by sashiko while review
In the Linux kernel, the following vulnerability has been resolved: v ...
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: fix zerocopy completion for multi-skb sends When a large message is fragmented into multiple skbs, the zerocopy uarg is only allocated and attached to the last skb in the loop. Non-final skbs carry pinned user pages with no completion tracking, so the kernel has no way to notify userspace when those pages are safe to reuse. If the loop breaks early the uarg is never allocated at all, leaking pinned pages with no completion notification. Fix this by following the approach used by TCP: allocate the zerocopy uarg (if not provided by the caller) before the send loop and attach it to every skb via skb_zcopy_set(), which takes a reference per skb. Each skb's completion properly decrements the refcount, and the notification only fires after the last skb is freed. On failure, if no data was sent, the uarg is cleanly aborted via net_zcopy_put_abort(). This issue was initially discovered by sashiko while rev...
Уязвимость файла net/vmw_vsock/virtio_transport_common.c ядра операционных систем Linux, позволяющая нарушителю вызвать отказ в обслуживании
EPSS
7.8 High
CVSS3