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CVE PROGRAM SOURCE RECORD9.3 Critical

CVE-2026-74310

vhost/net: complete zerocopy ubufs only once

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: vhost/net: complete zerocopy ubufs only once vhost-net initializes one ubuf_info per outstanding zerocopy TX descriptor and hands it to the backend socket. The networking stack may then clone a zerocopy skb before all skb references are released. For example, batman-adv fragmentation reaches skb_split(), which calls skb_zerocopy_clone() and increments the same ubuf_info refcount. vhost_zerocopy_complete() currently treats every ubuf callback as a completed vhost descriptor. It dereferences ubuf->ctx, writes the descriptor completion state, and drops the vhost_net_ubuf_ref even when the callback only releases a cloned skb reference. A backend reset can therefore wait for and free the vhost_net_ubuf_ref while another cloned skb still carries the same ubuf_info. A later completion then dereferences the freed ubufs pointer. KASAN reports the stale completion as: BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x1d7/0x1f0 BUG: KASAN: slab-use-after-free in vhost_zerocopy_complete+0x101/0x1f0 vhost_zerocopy_complete skb_copy_ubufs __dev_forward_skb2 veth_xmit The freed object was allocated from vhost_net_ioctl() while setting the backend and freed through kfree_rcu()/kvfree_rcu_bulk after backend removal, while delayed skb completion still reached vhost_zerocopy_complete(). Honor the generic ubuf_info refcount before touching vhost state, and run the vhost descriptor completion only for the final ubuf reference. This matches the msg_zerocopy_complete() ownership rule for cloned zerocopy skbs.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • bab632d69ee48a106e779b60cc01adfe80a72807 to < ea71f873423fb73e66ad88936d6759ac0ad4aa53affected
  • bab632d69ee48a106e779b60cc01adfe80a72807 to < 6445b945024f4c7675ae5352b2d5885cb1deea71affected
  • bab632d69ee48a106e779b60cc01adfe80a72807 to < a9f8a1d2e3ff511eafd4c5462481950c2f4d2b5daffected
  • bab632d69ee48a106e779b60cc01adfe80a72807 to < 321c73baf54d971ce3771fea275c98a247f7ee35affected
  • bab632d69ee48a106e779b60cc01adfe80a72807 to < c069437924663539a93a1e5afe90838d9ccee284affected
  • bab632d69ee48a106e779b60cc01adfe80a72807 to < 8f6898fe80794f2d7c3d38c1158c806e4074a1c4affected

Linux Linux

Default version status: affected

  • 3.1affected
  • 0 to < 3.1unaffected
  • 6.1.178 to ≤ 6.1.*unaffected
  • 6.6.145 to ≤ 6.6.*unaffected
  • 6.12.97 to ≤ 6.12.*unaffected
  • 6.18.40 to ≤ 6.18.*unaffected
  • 7.1.5 to ≤ 7.1.*unaffected
  • 7.2 to ≤ *unaffected

References