CVE-2026-97611

In the Linux kernel, the following vulnerability has been resolved:

net: openvswitch: fix use-after-free of the flow table mask array

tbl_mask_array_realloc() retires the old mask_array before it stops being reachable:

old = ovsl_dereference(tbl->mask_array);
if (old) {
	...
	call_rcu(&old->rcu, mask_array_rcu_cb);
}

rcu_assign_pointer(tbl->mask_array, new);

call_rcu() only waits for read-side critical sections already in flight. tbl->mask_array still points at old between the call_rcu() and the rcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in that window picks up old in a fresh critical section that the pending grace period does not cover.

tbl_mask_array_realloc() runs in process context under ovs_mutex, so the window is preemptible and can outlast the grace period. Then mask_array_rcu_cb() frees old before the swap runs:

BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0 Read of size 8 at addr ffff888020b3e018 by task poc/741 flow_lookup.constprop.0+0x2bf/0x2f0 ovs_flow_tbl_lookup_stats+0x4a3/0x5c0 ovs_dp_process_packet+0x19c/0x710 ovs_vport_receive+0x243/0x390 internal_dev_xmit+0x81/0x170 Freed by task 728: kfree+0x16a/0x4e0 rcu_core+0x853/0x1030

Publish the new array before retiring the old one. The kfree_rcu() that call_rcu() replaced ran after the swap.

Affected Software

References

• https://git.kernel.org/stable/c/017dbbf0d6c319a487f68e22f56d91fc787d5525
• https://git.kernel.org/stable/c/035e9c3722067648a99010711d0ce81f42572ef4
• https://git.kernel.org/stable/c/4016ead17acd75312c066ecd47c4b7f0a81ceaa2
• https://git.kernel.org/stable/c/4c98b492e9ed63f9ca3e23566d9a6a4f235944f4
• https://git.kernel.org/stable/c/76678217cdabc41e3c74c23b45b62086ffb8fe7a
• https://git.kernel.org/stable/c/a0d18d21d48a551f82ee344e50efb8a682161489
• https://git.kernel.org/stable/c/ba4ba11ed6eb8972c69070417fc27b48deb002e8
• https://git.kernel.org/stable/c/cd982e11684def5d4a9fcfd5354de09032828414