CVE-2025-40186 (GCVE-0-2025-40186)
Vulnerability from cvelistv5
Published
2025-11-12 21:56
Modified
2025-11-12 21:56
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: tcp: Don't call reqsk_fastopen_remove() in tcp_conn_request(). syzbot reported the splat below in tcp_conn_request(). [0] If a listener is close()d while a TFO socket is being processed in tcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk->sk and calls inet_child_forget(), which calls tcp_disconnect() for the TFO socket. After the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(), where reqsk_put() is called due to !reqsk->sk. Then, reqsk_fastopen_remove() in tcp_conn_request() decrements the last req->rsk_refcnt and frees reqsk, and __reqsk_free() at the drop_and_free label causes the refcount underflow for the listener and double-free of the reqsk. Let's remove reqsk_fastopen_remove() in tcp_conn_request(). Note that other callers make sure tp->fastopen_rsk is not NULL. [0]: refcount_t: underflow; use-after-free. WARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28) Modules linked in: CPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:refcount_warn_saturate (lib/refcount.c:28) Code: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff <0f> 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6 RSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246 RAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900 RDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280 RBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280 R10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100 R13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8 FS: 00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000180 CR3: 000000000dbbe006 CR4: 0000000000372ef0 Call Trace: <IRQ> tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301) tcp_rcv_state_process (net/ipv4/tcp_input.c:6708) tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670) tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906) ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438) ip6_input (net/ipv6/ip6_input.c:500) ipv6_rcv (net/ipv6/ip6_input.c:311) __netif_receive_skb (net/core/dev.c:6104) process_backlog (net/core/dev.c:6456) __napi_poll (net/core/dev.c:7506) net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696) handle_softirqs (kernel/softirq.c:579) do_softirq (kernel/softirq.c:480) </IRQ>
References
Impacted products
Vendor Product Version
Linux Linux Version: 7ec092a91ff351dcde89c23e795b73a328274db6
Version: a4378dedd6e07e62f2fccb17d78c9665718763d0
Version: 33a4fdf0b4a25f8ce65380c3b0136b407ca57609
Version: 17d699727577814198d744d6afe54735c6b54c99
Version: dfd06131107e7b699ef1e2a24ed2f7d17c917753
Version: fa4749c065644af4db496b338452a69a3e5147d9
Version: 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01
Version: 45c8a6cc2bcd780e634a6ba8e46bffbdf1fc5c01
Version: ae313d14b45eca7a6bb29cb9bf396d977e7d28fb
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{
  "containers": {
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          "vendor": "Linux",
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              "status": "unaffected",
              "version": "6.18-rc1",
              "versionType": "original_commit_for_fix"
            }
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      "cpeApplicability": [
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          "nodes": [
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                  "vulnerable": true
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                  "versionEndExcluding": "5.10.246",
                  "versionStartIncluding": "5.10.245",
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                  "vulnerable": true
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                  "vulnerable": true
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                {
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                  "vulnerable": true
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                  "versionEndExcluding": "6.17.4",
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                  "vulnerable": true
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                  "versionEndExcluding": "6.18-rc1",
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntcp: Don\u0027t call reqsk_fastopen_remove() in tcp_conn_request().\n\nsyzbot reported the splat below in tcp_conn_request(). [0]\n\nIf a listener is close()d while a TFO socket is being processed in\ntcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk-\u003esk\nand calls inet_child_forget(), which calls tcp_disconnect() for the\nTFO socket.\n\nAfter the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),\nwhere reqsk_put() is called due to !reqsk-\u003esk.\n\nThen, reqsk_fastopen_remove() in tcp_conn_request() decrements the\nlast req-\u003ersk_refcnt and frees reqsk, and __reqsk_free() at the\ndrop_and_free label causes the refcount underflow for the listener\nand double-free of the reqsk.\n\nLet\u0027s remove reqsk_fastopen_remove() in tcp_conn_request().\n\nNote that other callers make sure tp-\u003efastopen_rsk is not NULL.\n\n[0]:\nrefcount_t: underflow; use-after-free.\nWARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28)\nModules linked in:\nCPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025\nRIP: 0010:refcount_warn_saturate (lib/refcount.c:28)\nCode: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff \u003c0f\u003e 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6\nRSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246\nRAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900\nRDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280\nRBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280\nR10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100\nR13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8\nFS:  00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: 0000200000000180 CR3: 000000000dbbe006 CR4: 0000000000372ef0\nCall Trace:\n \u003cIRQ\u003e\n tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301)\n tcp_rcv_state_process (net/ipv4/tcp_input.c:6708)\n tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670)\n tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906)\n ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438)\n ip6_input (net/ipv6/ip6_input.c:500)\n ipv6_rcv (net/ipv6/ip6_input.c:311)\n __netif_receive_skb (net/core/dev.c:6104)\n process_backlog (net/core/dev.c:6456)\n __napi_poll (net/core/dev.c:7506)\n net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696)\n handle_softirqs (kernel/softirq.c:579)\n do_softirq (kernel/softirq.c:480)\n \u003c/IRQ\u003e"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-11-12T21:56:29.033Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/e359b742eac1eac75cff4e38ee2e8cea492acd9b"
        },
        {
          "url": "https://git.kernel.org/stable/c/ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d"
        },
        {
          "url": "https://git.kernel.org/stable/c/eb85ad5f23268d64b037bfb545cbcba3752f90c7"
        },
        {
          "url": "https://git.kernel.org/stable/c/643a94b0cf767325e953591c212be2eb826b9d7f"
        },
        {
          "url": "https://git.kernel.org/stable/c/422c1c173c39bbbae1e0eaaf8aefe40b2596233b"
        },
        {
          "url": "https://git.kernel.org/stable/c/c11ace909e873118295e9eb22dc8c58b0b50eb32"
        },
        {
          "url": "https://git.kernel.org/stable/c/64dc47a13aa3d9daf7cec29b44dca8e22a6aea15"
        },
        {
          "url": "https://git.kernel.org/stable/c/2e7cbbbe3d61c63606994b7ff73c72537afe2e1c"
        }
      ],
      "title": "tcp: Don\u0027t call reqsk_fastopen_remove() in tcp_conn_request().",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40186",
    "datePublished": "2025-11-12T21:56:29.033Z",
    "dateReserved": "2025-04-16T07:20:57.177Z",
    "dateUpdated": "2025-11-12T21:56:29.033Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40186\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-11-12T22:15:45.443\",\"lastModified\":\"2025-11-14T16:42:30.503\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\ntcp: Don\u0027t call reqsk_fastopen_remove() in tcp_conn_request().\\n\\nsyzbot reported the splat below in tcp_conn_request(). [0]\\n\\nIf a listener is close()d while a TFO socket is being processed in\\ntcp_conn_request(), inet_csk_reqsk_queue_add() does not set reqsk-\u003esk\\nand calls inet_child_forget(), which calls tcp_disconnect() for the\\nTFO socket.\\n\\nAfter the cited commit, tcp_disconnect() calls reqsk_fastopen_remove(),\\nwhere reqsk_put() is called due to !reqsk-\u003esk.\\n\\nThen, reqsk_fastopen_remove() in tcp_conn_request() decrements the\\nlast req-\u003ersk_refcnt and frees reqsk, and __reqsk_free() at the\\ndrop_and_free label causes the refcount underflow for the listener\\nand double-free of the reqsk.\\n\\nLet\u0027s remove reqsk_fastopen_remove() in tcp_conn_request().\\n\\nNote that other callers make sure tp-\u003efastopen_rsk is not NULL.\\n\\n[0]:\\nrefcount_t: underflow; use-after-free.\\nWARNING: CPU: 12 PID: 5563 at lib/refcount.c:28 refcount_warn_saturate (lib/refcount.c:28)\\nModules linked in:\\nCPU: 12 UID: 0 PID: 5563 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full)\\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025\\nRIP: 0010:refcount_warn_saturate (lib/refcount.c:28)\\nCode: ab e8 8e b4 98 ff 0f 0b c3 cc cc cc cc cc 80 3d a4 e4 d6 01 00 75 9c c6 05 9b e4 d6 01 01 48 c7 c7 e8 df fb ab e8 6a b4 98 ff \u003c0f\u003e 0b e9 03 5b 76 00 cc 80 3d 7d e4 d6 01 00 0f 85 74 ff ff ff c6\\nRSP: 0018:ffffa79fc0304a98 EFLAGS: 00010246\\nRAX: d83af4db1c6b3900 RBX: ffff9f65c7a69020 RCX: d83af4db1c6b3900\\nRDX: 0000000000000000 RSI: 00000000ffff7fff RDI: ffffffffac78a280\\nRBP: 000000009d781b60 R08: 0000000000007fff R09: ffffffffac6ca280\\nR10: 0000000000017ffd R11: 0000000000000004 R12: ffff9f65c7b4f100\\nR13: ffff9f65c7d23c00 R14: ffff9f65c7d26000 R15: ffff9f65c7a64ef8\\nFS:  00007f9f962176c0(0000) GS:ffff9f65fcf00000(0000) knlGS:0000000000000000\\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\nCR2: 0000200000000180 CR3: 000000000dbbe006 CR4: 0000000000372ef0\\nCall Trace:\\n \u003cIRQ\u003e\\n tcp_conn_request (./include/linux/refcount.h:400 ./include/linux/refcount.h:432 ./include/linux/refcount.h:450 ./include/net/sock.h:1965 ./include/net/request_sock.h:131 net/ipv4/tcp_input.c:7301)\\n tcp_rcv_state_process (net/ipv4/tcp_input.c:6708)\\n tcp_v6_do_rcv (net/ipv6/tcp_ipv6.c:1670)\\n tcp_v6_rcv (net/ipv6/tcp_ipv6.c:1906)\\n ip6_protocol_deliver_rcu (net/ipv6/ip6_input.c:438)\\n ip6_input (net/ipv6/ip6_input.c:500)\\n ipv6_rcv (net/ipv6/ip6_input.c:311)\\n __netif_receive_skb (net/core/dev.c:6104)\\n process_backlog (net/core/dev.c:6456)\\n __napi_poll (net/core/dev.c:7506)\\n net_rx_action (net/core/dev.c:7569 net/core/dev.c:7696)\\n handle_softirqs (kernel/softirq.c:579)\\n do_softirq (kernel/softirq.c:480)\\n \u003c/IRQ\u003e\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2e7cbbbe3d61c63606994b7ff73c72537afe2e1c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/422c1c173c39bbbae1e0eaaf8aefe40b2596233b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/643a94b0cf767325e953591c212be2eb826b9d7f\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/64dc47a13aa3d9daf7cec29b44dca8e22a6aea15\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c11ace909e873118295e9eb22dc8c58b0b50eb32\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/e359b742eac1eac75cff4e38ee2e8cea492acd9b\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/eb85ad5f23268d64b037bfb545cbcba3752f90c7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/ff6a8883f96a5bc74241ce5b3d431a6dcfa2124d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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