CVE-2026-53365

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 skbs 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.

Weakness

The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Affected Software

Potential Mitigations

• Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
• For example, glibc in Linux provides protection against free of invalid pointers.
• When using Xcode to target OS X or iOS, enable automatic reference counting (ARC) [REF-391].
• To help correctly and consistently manage memory when programming in C++, consider using a smart pointer class such as std::auto_ptr (defined by ISO/IEC ISO/IEC 14882:2003), std::shared_ptr and std::unique_ptr (specified by an upcoming revision of the C++ standard, informally referred to as C++ 1x), or equivalent solutions such as Boost.

References

• https://git.kernel.org/stable/c/293fe8f2d1b5ac464ca16a8eba09571bbbb34ba9
• https://git.kernel.org/stable/c/76b995bc57bd90cb6e954e1966fbd8786da47f0d
• https://git.kernel.org/stable/c/ae38d9179190a956e2a87a69ef1dd6f451b51c4d
• https://git.kernel.org/stable/c/b3155f2b78db21e99256bcf7eb902f24ff6d5338