Linux Kernel vsock/virtio: Zerocopy Multi-skb Completion Tracking
CVE-2026-53365 Published on July 13, 2026
vsock/virtio: fix zerocopy completion for multi-skb sends
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.
Products Associated with CVE-2026-53365
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Affected Versions
Linux:- Version 581512a6dc939ef122e49336626ae159f3b8a345 and below 76b995bc57bd90cb6e954e1966fbd8786da47f0d is affected.
- Version 581512a6dc939ef122e49336626ae159f3b8a345 and below b3155f2b78db21e99256bcf7eb902f24ff6d5338 is affected.
- Version 581512a6dc939ef122e49336626ae159f3b8a345 and below ae38d9179190a956e2a87a69ef1dd6f451b51c4d is affected.
- Version 6.7 is affected.
- Before 6.7 is unaffected.
- Version 6.18.34, <= 6.18.* is unaffected.
- Version 7.0.11, <= 7.0.* is unaffected.
- Version 7.1, <= * is unaffected.