CVE-2023-53809 (GCVE-0-2023-53809)

Vulnerability from cvelistv5 – Published: 2025-12-09 00:01 – Updated: 2025-12-09 00:01
VLAI?
Summary
In the Linux kernel, the following vulnerability has been resolved: l2tp: Avoid possible recursive deadlock in l2tp_tunnel_register() When a file descriptor of pppol2tp socket is passed as file descriptor of UDP socket, a recursive deadlock occurs in l2tp_tunnel_register(). This situation is reproduced by the following program: int main(void) { int sock; struct sockaddr_pppol2tp addr; sock = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP); if (sock < 0) { perror("socket"); return 1; } addr.sa_family = AF_PPPOX; addr.sa_protocol = PX_PROTO_OL2TP; addr.pppol2tp.pid = 0; addr.pppol2tp.fd = sock; addr.pppol2tp.addr.sin_family = PF_INET; addr.pppol2tp.addr.sin_port = htons(0); addr.pppol2tp.addr.sin_addr.s_addr = inet_addr("192.168.0.1"); addr.pppol2tp.s_tunnel = 1; addr.pppol2tp.s_session = 0; addr.pppol2tp.d_tunnel = 0; addr.pppol2tp.d_session = 0; if (connect(sock, (const struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("connect"); return 1; } return 0; } This program causes the following lockdep warning: ============================================ WARNING: possible recursive locking detected 6.2.0-rc5-00205-gc96618275234 #56 Not tainted -------------------------------------------- repro/8607 is trying to acquire lock: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x2b7/0x11c0 but task is already holding lock: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(sk_lock-AF_PPPOX); lock(sk_lock-AF_PPPOX); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by repro/8607: #0: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30 stack backtrace: CPU: 0 PID: 8607 Comm: repro Not tainted 6.2.0-rc5-00205-gc96618275234 #56 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x100/0x178 __lock_acquire.cold+0x119/0x3b9 ? lockdep_hardirqs_on_prepare+0x410/0x410 lock_acquire+0x1e0/0x610 ? l2tp_tunnel_register+0x2b7/0x11c0 ? lock_downgrade+0x710/0x710 ? __fget_files+0x283/0x3e0 lock_sock_nested+0x3a/0xf0 ? l2tp_tunnel_register+0x2b7/0x11c0 l2tp_tunnel_register+0x2b7/0x11c0 ? sprintf+0xc4/0x100 ? l2tp_tunnel_del_work+0x6b0/0x6b0 ? debug_object_deactivate+0x320/0x320 ? lockdep_init_map_type+0x16d/0x7a0 ? lockdep_init_map_type+0x16d/0x7a0 ? l2tp_tunnel_create+0x2bf/0x4b0 ? l2tp_tunnel_create+0x3c6/0x4b0 pppol2tp_connect+0x14e1/0x1a30 ? pppol2tp_put_sk+0xd0/0xd0 ? aa_sk_perm+0x2b7/0xa80 ? aa_af_perm+0x260/0x260 ? bpf_lsm_socket_connect+0x9/0x10 ? pppol2tp_put_sk+0xd0/0xd0 __sys_connect_file+0x14f/0x190 __sys_connect+0x133/0x160 ? __sys_connect_file+0x190/0x190 ? lockdep_hardirqs_on+0x7d/0x100 ? ktime_get_coarse_real_ts64+0x1b7/0x200 ? ktime_get_coarse_real_ts64+0x147/0x200 ? __audit_syscall_entry+0x396/0x500 __x64_sys_connect+0x72/0xb0 do_syscall_64+0x38/0xb0 entry_SYSCALL_64_after_hwframe+0x63/0xcd This patch fixes the issue by getting/creating the tunnel before locking the pppol2tp socket.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 2d77e5c0ad79004b5ef901895437e9cce6dfcc7e , < 4a413d360959962995e16a899cf2b9ef53e9fcb9 (git)
Affected: 77e8ed776cdb1a24b2aab8fe7c6f1f154235e1ce , < f6df58aa15f7d469f69b1dd21b001ff483255244 (git)
Affected: cef0845b6dcfa2f6c2c832e7f9622551456c741d , < 4bb736b40475528ac1aa8c98b368563618488a70 (git)
Affected: 0b2c59720e65885a394a017d0cf9cab118914682 , < 5370647dd745bb3d8f37057006be207ddd8e9314 (git)
Affected: 0b2c59720e65885a394a017d0cf9cab118914682 , < 9ca5e7ecab064f1f47da07f7c1ddf40e4bc0e5ac (git)
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    Linux Linux Affected: 6.2
Unaffected: 0 , < 6.2 (semver)
Unaffected: 5.10.173 , ≤ 5.10.* (semver)
Unaffected: 5.15.99 , ≤ 5.15.* (semver)
Unaffected: 6.1.16 , ≤ 6.1.* (semver)
Unaffected: 6.2.3 , ≤ 6.2.* (semver)
Unaffected: 6.3 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_ppp.c"
          ],
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              "versionType": "git"
            },
            {
              "lessThan": "9ca5e7ecab064f1f47da07f7c1ddf40e4bc0e5ac",
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              "version": "0b2c59720e65885a394a017d0cf9cab118914682",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/l2tp/l2tp_ppp.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.2"
            },
            {
              "lessThan": "6.2",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.173",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.99",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.16",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.2.*",
              "status": "unaffected",
              "version": "6.2.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.173",
                  "versionStartIncluding": "5.10.166",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.99",
                  "versionStartIncluding": "5.15.91",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.16",
                  "versionStartIncluding": "6.1.9",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.2.3",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.3",
                  "versionStartIncluding": "6.2",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nl2tp: Avoid possible recursive deadlock in l2tp_tunnel_register()\n\nWhen a file descriptor of pppol2tp socket is passed as file descriptor\nof UDP socket, a recursive deadlock occurs in l2tp_tunnel_register().\nThis situation is reproduced by the following program:\n\nint main(void)\n{\n\tint sock;\n\tstruct sockaddr_pppol2tp addr;\n\n\tsock = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);\n\tif (sock \u003c 0) {\n\t\tperror(\"socket\");\n\t\treturn 1;\n\t}\n\n\taddr.sa_family = AF_PPPOX;\n\taddr.sa_protocol = PX_PROTO_OL2TP;\n\taddr.pppol2tp.pid = 0;\n\taddr.pppol2tp.fd = sock;\n\taddr.pppol2tp.addr.sin_family = PF_INET;\n\taddr.pppol2tp.addr.sin_port = htons(0);\n\taddr.pppol2tp.addr.sin_addr.s_addr = inet_addr(\"192.168.0.1\");\n\taddr.pppol2tp.s_tunnel = 1;\n\taddr.pppol2tp.s_session = 0;\n\taddr.pppol2tp.d_tunnel = 0;\n\taddr.pppol2tp.d_session = 0;\n\n\tif (connect(sock, (const struct sockaddr *)\u0026addr, sizeof(addr)) \u003c 0) {\n\t\tperror(\"connect\");\n\t\treturn 1;\n\t}\n\n\treturn 0;\n}\n\nThis program causes the following lockdep warning:\n\n ============================================\n WARNING: possible recursive locking detected\n 6.2.0-rc5-00205-gc96618275234 #56 Not tainted\n --------------------------------------------\n repro/8607 is trying to acquire lock:\n ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x2b7/0x11c0\n\n but task is already holding lock:\n ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30\n\n other info that might help us debug this:\n  Possible unsafe locking scenario:\n\n        CPU0\n        ----\n   lock(sk_lock-AF_PPPOX);\n   lock(sk_lock-AF_PPPOX);\n\n  *** DEADLOCK ***\n\n  May be due to missing lock nesting notation\n\n 1 lock held by repro/8607:\n  #0: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30\n\n stack backtrace:\n CPU: 0 PID: 8607 Comm: repro Not tainted 6.2.0-rc5-00205-gc96618275234 #56\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014\n Call Trace:\n  \u003cTASK\u003e\n  dump_stack_lvl+0x100/0x178\n  __lock_acquire.cold+0x119/0x3b9\n  ? lockdep_hardirqs_on_prepare+0x410/0x410\n  lock_acquire+0x1e0/0x610\n  ? l2tp_tunnel_register+0x2b7/0x11c0\n  ? lock_downgrade+0x710/0x710\n  ? __fget_files+0x283/0x3e0\n  lock_sock_nested+0x3a/0xf0\n  ? l2tp_tunnel_register+0x2b7/0x11c0\n  l2tp_tunnel_register+0x2b7/0x11c0\n  ? sprintf+0xc4/0x100\n  ? l2tp_tunnel_del_work+0x6b0/0x6b0\n  ? debug_object_deactivate+0x320/0x320\n  ? lockdep_init_map_type+0x16d/0x7a0\n  ? lockdep_init_map_type+0x16d/0x7a0\n  ? l2tp_tunnel_create+0x2bf/0x4b0\n  ? l2tp_tunnel_create+0x3c6/0x4b0\n  pppol2tp_connect+0x14e1/0x1a30\n  ? pppol2tp_put_sk+0xd0/0xd0\n  ? aa_sk_perm+0x2b7/0xa80\n  ? aa_af_perm+0x260/0x260\n  ? bpf_lsm_socket_connect+0x9/0x10\n  ? pppol2tp_put_sk+0xd0/0xd0\n  __sys_connect_file+0x14f/0x190\n  __sys_connect+0x133/0x160\n  ? __sys_connect_file+0x190/0x190\n  ? lockdep_hardirqs_on+0x7d/0x100\n  ? ktime_get_coarse_real_ts64+0x1b7/0x200\n  ? ktime_get_coarse_real_ts64+0x147/0x200\n  ? __audit_syscall_entry+0x396/0x500\n  __x64_sys_connect+0x72/0xb0\n  do_syscall_64+0x38/0xb0\n  entry_SYSCALL_64_after_hwframe+0x63/0xcd\n\nThis patch fixes the issue by getting/creating the tunnel before\nlocking the pppol2tp socket."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-09T00:01:07.120Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/4a413d360959962995e16a899cf2b9ef53e9fcb9"
        },
        {
          "url": "https://git.kernel.org/stable/c/f6df58aa15f7d469f69b1dd21b001ff483255244"
        },
        {
          "url": "https://git.kernel.org/stable/c/4bb736b40475528ac1aa8c98b368563618488a70"
        },
        {
          "url": "https://git.kernel.org/stable/c/5370647dd745bb3d8f37057006be207ddd8e9314"
        },
        {
          "url": "https://git.kernel.org/stable/c/9ca5e7ecab064f1f47da07f7c1ddf40e4bc0e5ac"
        }
      ],
      "title": "l2tp: Avoid possible recursive deadlock in l2tp_tunnel_register()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2023-53809",
    "datePublished": "2025-12-09T00:01:07.120Z",
    "dateReserved": "2025-12-08T23:58:35.276Z",
    "dateUpdated": "2025-12-09T00:01:07.120Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2023-53809\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-09T01:16:52.940\",\"lastModified\":\"2025-12-09T18:37:13.640\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nl2tp: Avoid possible recursive deadlock in l2tp_tunnel_register()\\n\\nWhen a file descriptor of pppol2tp socket is passed as file descriptor\\nof UDP socket, a recursive deadlock occurs in l2tp_tunnel_register().\\nThis situation is reproduced by the following program:\\n\\nint main(void)\\n{\\n\\tint sock;\\n\\tstruct sockaddr_pppol2tp addr;\\n\\n\\tsock = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);\\n\\tif (sock \u003c 0) {\\n\\t\\tperror(\\\"socket\\\");\\n\\t\\treturn 1;\\n\\t}\\n\\n\\taddr.sa_family = AF_PPPOX;\\n\\taddr.sa_protocol = PX_PROTO_OL2TP;\\n\\taddr.pppol2tp.pid = 0;\\n\\taddr.pppol2tp.fd = sock;\\n\\taddr.pppol2tp.addr.sin_family = PF_INET;\\n\\taddr.pppol2tp.addr.sin_port = htons(0);\\n\\taddr.pppol2tp.addr.sin_addr.s_addr = inet_addr(\\\"192.168.0.1\\\");\\n\\taddr.pppol2tp.s_tunnel = 1;\\n\\taddr.pppol2tp.s_session = 0;\\n\\taddr.pppol2tp.d_tunnel = 0;\\n\\taddr.pppol2tp.d_session = 0;\\n\\n\\tif (connect(sock, (const struct sockaddr *)\u0026addr, sizeof(addr)) \u003c 0) {\\n\\t\\tperror(\\\"connect\\\");\\n\\t\\treturn 1;\\n\\t}\\n\\n\\treturn 0;\\n}\\n\\nThis program causes the following lockdep warning:\\n\\n ============================================\\n WARNING: possible recursive locking detected\\n 6.2.0-rc5-00205-gc96618275234 #56 Not tainted\\n --------------------------------------------\\n repro/8607 is trying to acquire lock:\\n ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: l2tp_tunnel_register+0x2b7/0x11c0\\n\\n but task is already holding lock:\\n ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30\\n\\n other info that might help us debug this:\\n  Possible unsafe locking scenario:\\n\\n        CPU0\\n        ----\\n   lock(sk_lock-AF_PPPOX);\\n   lock(sk_lock-AF_PPPOX);\\n\\n  *** DEADLOCK ***\\n\\n  May be due to missing lock nesting notation\\n\\n 1 lock held by repro/8607:\\n  #0: ffff8880213c8130 (sk_lock-AF_PPPOX){+.+.}-{0:0}, at: pppol2tp_connect+0xa82/0x1a30\\n\\n stack backtrace:\\n CPU: 0 PID: 8607 Comm: repro Not tainted 6.2.0-rc5-00205-gc96618275234 #56\\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014\\n Call Trace:\\n  \u003cTASK\u003e\\n  dump_stack_lvl+0x100/0x178\\n  __lock_acquire.cold+0x119/0x3b9\\n  ? lockdep_hardirqs_on_prepare+0x410/0x410\\n  lock_acquire+0x1e0/0x610\\n  ? l2tp_tunnel_register+0x2b7/0x11c0\\n  ? lock_downgrade+0x710/0x710\\n  ? __fget_files+0x283/0x3e0\\n  lock_sock_nested+0x3a/0xf0\\n  ? l2tp_tunnel_register+0x2b7/0x11c0\\n  l2tp_tunnel_register+0x2b7/0x11c0\\n  ? sprintf+0xc4/0x100\\n  ? l2tp_tunnel_del_work+0x6b0/0x6b0\\n  ? debug_object_deactivate+0x320/0x320\\n  ? lockdep_init_map_type+0x16d/0x7a0\\n  ? lockdep_init_map_type+0x16d/0x7a0\\n  ? l2tp_tunnel_create+0x2bf/0x4b0\\n  ? l2tp_tunnel_create+0x3c6/0x4b0\\n  pppol2tp_connect+0x14e1/0x1a30\\n  ? pppol2tp_put_sk+0xd0/0xd0\\n  ? aa_sk_perm+0x2b7/0xa80\\n  ? aa_af_perm+0x260/0x260\\n  ? bpf_lsm_socket_connect+0x9/0x10\\n  ? pppol2tp_put_sk+0xd0/0xd0\\n  __sys_connect_file+0x14f/0x190\\n  __sys_connect+0x133/0x160\\n  ? __sys_connect_file+0x190/0x190\\n  ? lockdep_hardirqs_on+0x7d/0x100\\n  ? ktime_get_coarse_real_ts64+0x1b7/0x200\\n  ? ktime_get_coarse_real_ts64+0x147/0x200\\n  ? __audit_syscall_entry+0x396/0x500\\n  __x64_sys_connect+0x72/0xb0\\n  do_syscall_64+0x38/0xb0\\n  entry_SYSCALL_64_after_hwframe+0x63/0xcd\\n\\nThis patch fixes the issue by getting/creating the tunnel before\\nlocking the pppol2tp socket.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/4a413d360959962995e16a899cf2b9ef53e9fcb9\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4bb736b40475528ac1aa8c98b368563618488a70\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5370647dd745bb3d8f37057006be207ddd8e9314\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9ca5e7ecab064f1f47da07f7c1ddf40e4bc0e5ac\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f6df58aa15f7d469f69b1dd21b001ff483255244\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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