CVE-2026-89487openvswitch: only skb_tx_error() a packet we are about to drop

Official description

In the Linux kernel, the following vulnerability has been resolved: openvswitch: only skb_tx_error() a packet we are about to drop queue_userspace_packet() borrows the packet skb -- it only copies it into a private netlink message (user_skb) and does not own it; on return do_execute_actions() keeps forwarding it through the flow's remaining actions. Its error path nevertheless calls skb_tx_error(skb), which via skb_zcopy_clear() does skb_shinfo(skb)->flags &= ~SKBFL_ALL_ZEROCOPY, stripping SKBFL_SHARED_FRAG from that live skb (skb_tx_error()'s kerneldoc says "skb must be freed afterwards"). For a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is what makes esp_input() skb_cow_data() before in-place AEAD; once it is stripped a later local ESP-in-UDP delivery decrypts in place over pages the sender does not own -- an unprivileged page-cache write (the "Fragnesia" primitive). do_execute_actions() ignores output_userspace()'s return value, so any action after a failed USERSPACE upcall inherits the stripped skb. Move the skb_tx_error() to the flow-miss drop path - the "default" branch of ovs_dp_process_packet()'s switch(error), before kfree_skb(). The call has been here since commit 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors") but was harmless until esp_input() began relying on SKBFL_SHARED_FRAG to gate in-place decrypt; only then did stripping it on a still-forwarded skb become a page-cache write primitive.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/5de5d554141a15b3f1f5c978fd9f7f4fd6d0600a
• https://git.kernel.org/stable/c/48db11e115d1b232edc5591604adc6eda95cd545
• https://git.kernel.org/stable/c/4477222e2916a18e273edc139c955ade6bbb7a69
• https://git.kernel.org/stable/c/4d5c460ef8754be1d43b16dbf02695b008b207d6
• https://git.kernel.org/stable/c/6767d70cf46f65807a6a4c4406a518e6c12e36ae
• https://git.kernel.org/stable/c/e41a59fc056f63a7a1f42788913c53cc48d744aa
• https://git.kernel.org/stable/c/5d85eef222cfd28e73deed7402c100229e8b9e6e
• https://git.kernel.org/stable/c/0dbc2398fca3bb33eda963849f865ddb1b3aa05e