mlxsw: spectrum_router: Fix neighbour use-after-free

{
  "id": "c05befc84f94cd35188576ca254cb9d0ab878693f185dd3a4183f33c8daaac68",
  "url": "https://osv.dev/vulnerability/CVE-2025-68801",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mlxsw: spectrum_router: Fix neighbour use-after-free",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mlxsw: spectrum_router: Fix neighbour use-after-free We sometimes observe use-after-free when dereferencing a neighbour [1]. The problem seems to be that the driver stores a pointer to the neighbour, but without holding a reference on it. A reference is only taken when the neighbour is used by a nexthop. Fix by simplifying the reference counting scheme. Always take a reference when storing a neighbour pointer in a neighbour entry. Avoid taking a referencing when the neighbour is used by a nexthop as the neighbour entry associated with the nexthop already holds a reference. Tested by running the test that uncovered the problem over 300 times. Without this patch the problem was reproduced after a handful of iterations. [1] BUG: KASAN: slab-use-after-free in mlxsw_sp_neigh_entry_update+0x2d4/0x310 Read of size 8 at addr ffff88817f8e3420 by task ip/3929 CPU: 3 UID: 0 PID: 3929 Comm: ip Not tainted 6.18.0-rc4-virtme-g36b21a067510 #3 PREEMPT(full) Hardware name: Nvidia SN5600/VMOD0013, BIOS 5.13 05/31/2023 Call Trace: dump_stack_lvl+0x6f/0xa0 print_address_description.constprop.0+0x6e/0x300 print_report+0xfc/0x1fb kasan_report+0xe4/0x110 mlxsw_sp_neigh_entry_update+0x2d4/0x310 mlxsw_sp_router_rif_gone_sync+0x35f/0x510 mlxsw_sp_rif_destroy+0x1ea/0x730 mlxsw_sp_inetaddr_port_vlan_event+0xa1/0x1b0 __mlxsw_sp_inetaddr_lag_event+0xcc/0x130 __mlxsw_sp_inetaddr_event+0xf5/0x3c0 mlxsw_sp_router_netdevice_event+0x1015/0x158",
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      "modified": "2026-10-28T02:30:30.822593132Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/4a3c569005f42ab5e5b2ad637132a33bf102cc08",
        "https://git.kernel.org/stable/c/675c5aeadf6472672c472dc0f26401e4fcfbf254",
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        "https://git.kernel.org/stable/c/9e0a0d9eeb0dbeba2c83fa837885b19b8b9230fc",
        "https://git.kernel.org/stable/c/a2dfe6758fc63e542105bee8b17a3a7485684db0",
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        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/68xxx/CVE-2025-68801.json",
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    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 497845,
  "published_at": "2026-01-13T15:29:10.349+00:00"
}