CVE-2026-64102 (GCVE-0-2026-64102)
Vulnerability from cvelistv5
Published
2026-07-19 15:40
Modified
2026-08-05 12:39
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Reject MPA FPDU length underflow before signed receive math A malicious connected siw peer can send an iWARP FPDU whose MPA length field (c_hdr->mpa_len, 16 bit big-endian, peer-controlled) is smaller than the fixed DDP/RDMAP header for the announced opcode. Soft-iWARP parses the full header in siw_get_hdr() based on iwarp_pktinfo[opcode] .hdr_len, but never compares mpa_len against that header length. siw_tcp_rx_data() then derives srx->fpdu_part_rem = be16_to_cpu(mpa_len) - fpdu_part_rcvd + MPA_HDR_SIZE; where fpdu_part_rcvd equals iwarp_pktinfo[opcode].hdr_len at this point. For a tagged WRITE (hdr_len 16, MPA_HDR_SIZE 2) the smallest on-wire mpa_len of 0 yields fpdu_part_rem = -14, and any mpa_len below hdr_len - MPA_HDR_SIZE underflows to a negative int. The signed value then flows into siw_proc_write()/siw_proc_rresp() as bytes = min(srx->fpdu_part_rem, srx->skb_new); is handed to siw_check_mem() as an int len (whose interval check addr + len > mem->va + mem->len is satisfied for a valid base when len is negative), and reaches siw_rx_data() -> siw_rx_kva() / siw_rx_umem() -> skb_copy_bits() as a signed copy length. The header copy branch in skb_copy_bits() promotes that to size_t, producing a multi-gigabyte read. KASAN under a KUnit harness that drives the real kernel TCP receive path -- a loopback AF_INET socketpair, the malformed FPDU written via kernel_sendmsg, sk_data_ready firing in softirq, tcp_read_sock dispatching to siw_tcp_rx_data -- reports: BUG: KASAN: use-after-free in skb_copy_bits+0x284/0x480 Read of size 4294967295 at addr ffff888... Call Trace: skb_copy_bits siw_rx_kva siw_rx_data siw_check_mem siw_proc_write siw_tcp_rx_data __tcp_read_sock siw_qp_llp_data_ready tcp_data_ready tcp_data_queue Add the missing invariant at the earliest point where the peer header is fully assembled. iwarp_pktinfo[*].hdr_len - MPA_HDR_SIZE is exactly the value the siw transmitter uses as the minimum mpa_len for each opcode (drivers/infiniband/sw/siw/siw_qp.c:33), so this matches the protocol contract. Out-of-range FPDUs terminate the connection with TERM_ERROR_LAYER_LLP / LLP_ETYPE_MPA / LLP_ECODE_FPDU_START -- which is RFC 5044 Section 8 error code 3 ("Marker and ULPDU Length fields do not agree on the start of an FPDU"), the correct framing-error class for this inconsistency.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
Version: 8b6a361b8c482f22ac99c3273285ff16b23fba91
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{
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          "programFiles": [
            "drivers/infiniband/sw/siw/siw_qp_rx.c"
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      ],
      "cpeApplicability": [
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          "nodes": [
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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\nRDMA/siw: Reject MPA FPDU length underflow before signed receive math\n\nA malicious connected siw peer can send an iWARP FPDU whose MPA length\nfield (c_hdr-\u003empa_len, 16 bit big-endian, peer-controlled) is smaller\nthan the fixed DDP/RDMAP header for the announced opcode. Soft-iWARP\nparses the full header in siw_get_hdr() based on iwarp_pktinfo[opcode]\n.hdr_len, but never compares mpa_len against that header length.\n\nsiw_tcp_rx_data() then derives\n\n    srx-\u003efpdu_part_rem = be16_to_cpu(mpa_len) - fpdu_part_rcvd\n                         + MPA_HDR_SIZE;\n\nwhere fpdu_part_rcvd equals iwarp_pktinfo[opcode].hdr_len at this\npoint. For a tagged WRITE (hdr_len 16, MPA_HDR_SIZE 2) the smallest\non-wire mpa_len of 0 yields fpdu_part_rem = -14, and any mpa_len below\nhdr_len - MPA_HDR_SIZE underflows to a negative int.\n\nThe signed value then flows into siw_proc_write()/siw_proc_rresp() as\n\n    bytes = min(srx-\u003efpdu_part_rem, srx-\u003eskb_new);\n\nis handed to siw_check_mem() as an int len (whose interval check\naddr + len \u003e mem-\u003eva + mem-\u003elen is satisfied for a valid base when\nlen is negative), and reaches siw_rx_data() -\u003e siw_rx_kva() /\nsiw_rx_umem() -\u003e skb_copy_bits() as a signed copy length. The header\ncopy branch in skb_copy_bits() promotes that to size_t, producing a\nmulti-gigabyte read.\n\nKASAN under a KUnit harness that drives the real kernel TCP receive\npath -- a loopback AF_INET socketpair, the malformed FPDU written via\nkernel_sendmsg, sk_data_ready firing in softirq, tcp_read_sock\ndispatching to siw_tcp_rx_data -- reports:\n\n    BUG: KASAN: use-after-free in skb_copy_bits+0x284/0x480\n    Read of size 4294967295 at addr ffff888...\n    Call Trace:\n     skb_copy_bits\n     siw_rx_kva\n     siw_rx_data\n     siw_check_mem\n     siw_proc_write\n     siw_tcp_rx_data\n     __tcp_read_sock\n     siw_qp_llp_data_ready\n     tcp_data_ready\n     tcp_data_queue\n\nAdd the missing invariant at the earliest point where the peer header\nis fully assembled. iwarp_pktinfo[*].hdr_len - MPA_HDR_SIZE is exactly\nthe value the siw transmitter uses as the minimum mpa_len for each\nopcode (drivers/infiniband/sw/siw/siw_qp.c:33), so this matches the\nprotocol contract. Out-of-range FPDUs terminate the connection with\nTERM_ERROR_LAYER_LLP / LLP_ETYPE_MPA / LLP_ECODE_FPDU_START -- which\nis RFC 5044 Section 8 error code 3 (\"Marker and ULPDU Length fields\ndo not agree on the start of an FPDU\"), the correct framing-error\nclass for this inconsistency."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - A remote attacker triggers this by sending a malformed iWARP FPDU over an established TCP connection; the kernel processes it in the TCP softirq receive path via siw_tcp_rx_data without any local access.\nAC:L - The attacker fully controls the peer-supplied mpa_len field and can reliably underflow fpdu_part_rem with a single crafted packet (e.g., mpa_len=0 on a tagged WRITE with hdr_len=16); no races or uncontrollable memory layout are required.\nPR:N - Exploitation requires only network reachability to a host running an iWARP listener (e.g., SMB Direct/RDMA-over-TCP on siw); completing the MPA/TCP handshake does not require any local account or elevated privileges on the victim system.\nUI:N - No victim user interaction is needed; the malformed FPDU is processed automatically when received on the connected TCP socket during normal kernel softirq handling.\nS:U - Impact is confined to kernel memory and RDMA-registered buffers on the victim host; this is standard in-kernel memory corruption without crossing a VM, container, or IOMMU security boundary.\nC:H - The negative copy length is promoted to a huge unsigned value in skb_copy_bits, producing a multi-gigabyte out-of-bounds read; KASAN confirmed use-after-free with a 4294967295-byte read, enabling arbitrary kernel memory disclosure.\nI:H - The same corrupted length drives skb_copy_bits writes into RDMA target memory (siw_rx_kva/siw_rx_umem) after siw_check_mem is bypassed by negative len, enabling out-of-bounds writes exploitable for memory corruption and potential code execution.\nA:H - KASAN reports use-after-free in skb_copy_bits during normal receive processing, and this class of kernel memory corruption reliably causes oops/panic or exploitable instability under attacker control."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:39:14.704Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/683f7cfbf514193d63c0efa079f3352bde84c2e0"
        },
        {
          "url": "https://git.kernel.org/stable/c/4a331582011d9e8089af8aa2a61ec6b4443bb245"
        },
        {
          "url": "https://git.kernel.org/stable/c/33a8b5e971e294ec2a7b74211c545e09efd8e9ac"
        },
        {
          "url": "https://git.kernel.org/stable/c/14553be882d9ce91749c9d64041de66e34ad8e70"
        },
        {
          "url": "https://git.kernel.org/stable/c/c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2"
        },
        {
          "url": "https://git.kernel.org/stable/c/1012896f4225e8f801ff3c1648023845b66dfb11"
        },
        {
          "url": "https://git.kernel.org/stable/c/775b4dc9618a99a1fa48b57554041a5dc17e1336"
        },
        {
          "url": "https://git.kernel.org/stable/c/0ce1bc9e46ecabe84772bb561e373c0d9876d6f2"
        }
      ],
      "title": "RDMA/siw: Reject MPA FPDU length underflow before signed receive math",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64102",
    "datePublished": "2026-07-19T15:40:06.776Z",
    "dateReserved": "2026-07-19T07:54:57.033Z",
    "dateUpdated": "2026-08-05T12:39:14.704Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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