{"id":"CVE-2026-64102","summary":"RDMA/siw: Reject MPA FPDU length underflow before signed receive math","details":"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.","modified":"2026-07-22T03:31:34.511321644Z","published":"2026-07-19T15:40:06.776Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64102.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0ce1bc9e46ecabe84772bb561e373c0d9876d6f2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1012896f4225e8f801ff3c1648023845b66dfb11"},{"type":"WEB","url":"https://git.kernel.org/stable/c/14553be882d9ce91749c9d64041de66e34ad8e70"},{"type":"WEB","url":"https://git.kernel.org/stable/c/33a8b5e971e294ec2a7b74211c545e09efd8e9ac"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4a331582011d9e8089af8aa2a61ec6b4443bb245"},{"type":"WEB","url":"https://git.kernel.org/stable/c/683f7cfbf514193d63c0efa079f3352bde84c2e0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/775b4dc9618a99a1fa48b57554041a5dc17e1336"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64102.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64102"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8b6a361b8c482f22ac99c3273285ff16b23fba91"},{"fixed":"683f7cfbf514193d63c0efa079f3352bde84c2e0"},{"fixed":"4a331582011d9e8089af8aa2a61ec6b4443bb245"},{"fixed":"33a8b5e971e294ec2a7b74211c545e09efd8e9ac"},{"fixed":"14553be882d9ce91749c9d64041de66e34ad8e70"},{"fixed":"c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2"},{"fixed":"1012896f4225e8f801ff3c1648023845b66dfb11"},{"fixed":"775b4dc9618a99a1fa48b57554041a5dc17e1336"},{"fixed":"0ce1bc9e46ecabe84772bb561e373c0d9876d6f2"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64102.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.3.0"},{"fixed":"5.10.258"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.209"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.175"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.142"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.92"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.34"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.0.11"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-64102.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}]}