GHSA-P256-HQVM-38XQ
Vulnerability from github – Published: 2026-09-25 12:31 – Updated: 2026-09-25 15:31In 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": [],
"aliases": [
"CVE-2026-97611"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-25T11:17:15Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: openvswitch: fix use-after-free of the flow table mask array\n\ntbl_mask_array_realloc() retires the old mask_array before it stops being\nreachable:\n\n\told = ovsl_dereference(tbl-\u003emask_array);\n\tif (old) {\n\t\t...\n\t\tcall_rcu(\u0026old-\u003ercu, mask_array_rcu_cb);\n\t}\n\n\trcu_assign_pointer(tbl-\u003emask_array, new);\n\ncall_rcu() only waits for read-side critical sections already in flight.\ntbl-\u003emask_array still points at old between the call_rcu() and the\nrcu_assign_pointer(), so a reader entering ovs_flow_tbl_lookup_stats() in\nthat window picks up old in a fresh critical section that the pending\ngrace period does not cover.\n\ntbl_mask_array_realloc() runs in process context under ovs_mutex, so the\nwindow is preemptible and can outlast the grace period. Then\nmask_array_rcu_cb() frees old before the swap runs:\n\n BUG: KASAN: slab-use-after-free in flow_lookup.constprop.0+0x2bf/0x2f0\n Read of size 8 at addr ffff888020b3e018 by task poc/741\n flow_lookup.constprop.0+0x2bf/0x2f0\n ovs_flow_tbl_lookup_stats+0x4a3/0x5c0\n ovs_dp_process_packet+0x19c/0x710\n ovs_vport_receive+0x243/0x390\n internal_dev_xmit+0x81/0x170\n Freed by task 728:\n kfree+0x16a/0x4e0\n rcu_core+0x853/0x1030\n\nPublish the new array before retiring the old one. The kfree_rcu() that\ncall_rcu() replaced ran after the swap.",
"id": "GHSA-p256-hqvm-38xq",
"modified": "2026-09-25T15:31:43Z",
"published": "2026-09-25T12:31:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97611"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/035e9c3722067648a99010711d0ce81f42572ef4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a0d18d21d48a551f82ee344e50efb8a682161489"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ba4ba11ed6eb8972c69070417fc27b48deb002e8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/cd982e11684def5d4a9fcfd5354de09032828414"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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