tcp: tcp_rtx_synack() can be called from process context

{
  "id": "daf453aaf4f75c329fc0100aca2e38b83f71f7af8e110ce3349706717404c5b2",
  "url": "https://osv.dev/vulnerability/CVE-2022-49372",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "tcp: tcp_rtx_synack() can be called from process context",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: tcp: tcp_rtx_synack() can be called from process context Laurent reported the enclosed report [1] This bug triggers with following coditions: 0) Kernel built with CONFIG_DEBUG_PREEMPT=y 1) A new passive FastOpen TCP socket is created. This FO socket waits for an ACK coming from client to be a complete ESTABLISHED one. 2) A socket operation on this socket goes through lock_sock() release_sock() dance. 3) While the socket is owned by the user in step 2), a retransmit of the SYN is received and stored in socket backlog. 4) At release_sock() time, the socket backlog is processed while in process context. 5) A SYNACK packet is cooked in response of the SYN retransmit. 6) -> tcp_rtx_synack() is called in process context. Before blamed commit, tcp_rtx_synack() was always called from BH handler, from a timer handler. Fix this by using TCP_INC_STATS() & NET_INC_STATS() which do not assume caller is in non preemptible context. [1] BUG: using __this_cpu_add() in preemptible [00000000] code: epollpep/2180 caller is tcp_rtx_synack.part.0+0x36/0xc0 CPU: 10 PID: 2180 Comm: epollpep Tainted: G OE 5.16.0-0.bpo.4-amd64 #1 Debian 5.16.12-1~bpo11+1 Hardware name: Supermicro SYS-5039MC-H8TRF/X11SCD-F, BIOS 1.7 11/23/2021 Call Trace: dump_stack_lvl+0x48/0x5e check_preemption_disabled+0xde/0xe0 tcp_rtx_synack.part.0+0x36/0xc0 tcp_rtx_synack+0x8d/0xa0 ? kmem_cache_alloc+0x2e0/0x3e0 ? apparmor_file_alloc_security+0x3b/0x1f0 inet_rtx_",
    "evidence": "osv:CVE-2022-49372",
    "products": [
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        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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        "affected_versions": []
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    ],
    "severity": "unknown",
    "structured": {
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      "aliases": [
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      "modified": "2026-10-28T02:30:23.499359393Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0a0f7f84148445c9f02f226928803a870139d820",
        "https://git.kernel.org/stable/c/0a375c822497ed6ad6b5da0792a12a6f1af10c0b",
        "https://git.kernel.org/stable/c/3db889f883e65bbd3b1401279bfc1e9ed255c481",
        "https://git.kernel.org/stable/c/58bd38cbc961fd799842b7be8c5222310f04b908",
        "https://git.kernel.org/stable/c/88cd232146207ff1d41dededed5e77c0d4438113",
        "https://git.kernel.org/stable/c/bdc28a8fb43cc476e33b11519235adb816ce00e8",
        "https://git.kernel.org/stable/c/c348b0f8d035fc4bdc040796889beec7218bd1b8",
        "https://git.kernel.org/stable/c/d05c2fdf8e10528bb6751bd95243e862d5402a9b",
        "https://git.kernel.org/stable/c/d8e1bc6029acac796293310aacef7b7336f35b6a",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/49xxx/CVE-2022-49372.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2022-49372",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2022/49xxx/CVE-2022-49372.json"
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        "value": "CVE-2022-49372",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 489887,
  "published_at": "2025-02-26T02:11:14.119+00:00"
}