Bug 2492282 (CVE-2026-52994)

Summary: CVE-2026-52994 kernel: vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's `vsock/virtio` component. This vulnerability involves an accounting error in the `MSG_ZEROCOPY` pinned-pages mechanism, where the system's resource limit for locked memory (`RLIMIT_MEMLOCK`) may not be properly enforced. This could allow a local attacker or a malicious virtual machine guest to bypass memory locking restrictions, potentially leading to resource exhaustion or a denial of service (DoS) condition.
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Description OSIDB Bzimport 2026-06-24 18:03:00 UTC 
In the Linux kernel, the following vulnerability has been resolved:

vsock/virtio: fix MSG_ZEROCOPY pinned-pages accounting

virtio_transport_init_zcopy_skb() uses iter->count as the size argument
for msg_zerocopy_realloc(), which in turn passes it to
mm_account_pinned_pages() for RLIMIT_MEMLOCK accounting. However, this
function is called after virtio_transport_fill_skb() has already consumed
the iterator via __zerocopy_sg_from_iter(), so on the last skb, iter->count
will be 0, skipping the RLIMIT_MEMLOCK enforcement.

Pass pkt_len (the total bytes being sent) as an explicit parameter to
virtio_transport_init_zcopy_skb() instead of reading the already-consumed
iter->count.

This matches TCP and UDP, which both call msg_zerocopy_realloc() with
the original message size.
Comment 1 Mauro Matteo Cascella 2026-06-25 15:03:53 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062445-CVE-2026-52994-fe3c@gregkh/T