CVE-2025-40123 (GCVE-0-2025-40123)
Vulnerability from cvelistv5
Published
2025-11-12 10:23
Modified
2025-11-12 10:23
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Enforce expected_attach_type for tailcall compatibility Yinhao et al. recently reported: Our fuzzer tool discovered an uninitialized pointer issue in the bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdp_buff object. The test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the entry point for bpf_prog_test_run_xdp() and its expected_attach_type can neither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot of a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP to pass xdp_is_valid_access() validation. The program returns struct xdp_md's egress_ifindex, and the latter is only allowed to be accessed under mentioned expected_attach_type. progB is then inserted into the tailcall which progA calls. The underlying issue goes beyond XDP though. Another example are programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well as sock_addr_func_proto() have different logic depending on the programs' expected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME should not be allowed doing a tailcall into a program which calls bpf_bind() out of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT. In short, specifying expected_attach_type allows to open up additional functionality or restrictions beyond what the basic bpf_prog_type enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expected_attach_type in __bpf_prog_map_compatible(). Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and cpu_map_bpf_prog_run*() which set up a new environment / context and therefore these situations are not prone to this issue.
References
Impacted products
Vendor Product Version
Linux Linux Version: 5e43f899b03a3492ce5fc44e8900becb04dae9c0
Version: 5e43f899b03a3492ce5fc44e8900becb04dae9c0
Version: 5e43f899b03a3492ce5fc44e8900becb04dae9c0
Version: 5e43f899b03a3492ce5fc44e8900becb04dae9c0
Version: 5e43f899b03a3492ce5fc44e8900becb04dae9c0
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/bpf.h",
            "kernel/bpf/core.c"
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          "vendor": "Linux",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Enforce expected_attach_type for tailcall compatibility\n\nYinhao et al. recently reported:\n\n  Our fuzzer tool discovered an uninitialized pointer issue in the\n  bpf_prog_test_run_xdp() function within the Linux kernel\u0027s BPF subsystem.\n  This leads to a NULL pointer dereference when a BPF program attempts to\n  deference the txq member of struct xdp_buff object.\n\nThe test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the\nentry point for bpf_prog_test_run_xdp() and its expected_attach_type can\nneither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot\nof a tailcall map it owns. progB\u0027s expected_attach_type must be BPF_XDP_DEVMAP\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md\u0027s\negress_ifindex, and the latter is only allowed to be accessed under mentioned\nexpected_attach_type. progB is then inserted into the tailcall which progA\ncalls.\n\nThe underlying issue goes beyond XDP though. Another example are programs\nof type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well\nas sock_addr_func_proto() have different logic depending on the programs\u0027\nexpected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME\nshould not be allowed doing a tailcall into a program which calls bpf_bind()\nout of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT.\n\nIn short, specifying expected_attach_type allows to open up additional\nfunctionality or restrictions beyond what the basic bpf_prog_type enables.\nThe use of tailcalls must not violate these constraints. Fix it by enforcing\nexpected_attach_type in __bpf_prog_map_compatible().\n\nNote that we only enforce this for tailcall maps, but not for BPF devmaps or\ncpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and\ncpu_map_bpf_prog_run*() which set up a new environment / context and therefore\nthese situations are not prone to this issue."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-11-12T10:23:19.589Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/a99de19128aec0913f3d529f529fbbff5edfaff8"
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        },
        {
          "url": "https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0"
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      ],
      "title": "bpf: Enforce expected_attach_type for tailcall compatibility",
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  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40123",
    "datePublished": "2025-11-12T10:23:19.589Z",
    "dateReserved": "2025-04-16T07:20:57.169Z",
    "dateUpdated": "2025-11-12T10:23:19.589Z",
    "state": "PUBLISHED"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2025-40123\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-11-12T11:15:41.807\",\"lastModified\":\"2025-11-12T16:19:12.850\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbpf: Enforce expected_attach_type for tailcall compatibility\\n\\nYinhao et al. recently reported:\\n\\n  Our fuzzer tool discovered an uninitialized pointer issue in the\\n  bpf_prog_test_run_xdp() function within the Linux kernel\u0027s BPF subsystem.\\n  This leads to a NULL pointer dereference when a BPF program attempts to\\n  deference the txq member of struct xdp_buff object.\\n\\nThe test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the\\nentry point for bpf_prog_test_run_xdp() and its expected_attach_type can\\nneither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot\\nof a tailcall map it owns. progB\u0027s expected_attach_type must be BPF_XDP_DEVMAP\\nto pass xdp_is_valid_access() validation. The program returns struct xdp_md\u0027s\\negress_ifindex, and the latter is only allowed to be accessed under mentioned\\nexpected_attach_type. progB is then inserted into the tailcall which progA\\ncalls.\\n\\nThe underlying issue goes beyond XDP though. Another example are programs\\nof type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well\\nas sock_addr_func_proto() have different logic depending on the programs\u0027\\nexpected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME\\nshould not be allowed doing a tailcall into a program which calls bpf_bind()\\nout of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT.\\n\\nIn short, specifying expected_attach_type allows to open up additional\\nfunctionality or restrictions beyond what the basic bpf_prog_type enables.\\nThe use of tailcalls must not violate these constraints. Fix it by enforcing\\nexpected_attach_type in __bpf_prog_map_compatible().\\n\\nNote that we only enforce this for tailcall maps, but not for BPF devmaps or\\ncpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and\\ncpu_map_bpf_prog_run*() which set up a new environment / context and therefore\\nthese situations are not prone to this issue.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/a99de19128aec0913f3d529f529fbbff5edfaff8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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