RDMA/siw: Reject MPA FPDU length underflow before signed receive math

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Summary

CVECVE-2026-64102
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:51 UTC
Updated2026-07-19 16:17:51 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 683f7cfbf514193d63c0efa079f3352bde84c2e0 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 4a331582011d9e8089af8aa2a61ec6b4443bb245 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 33a8b5e971e294ec2a7b74211c545e09efd8e9ac git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 14553be882d9ce91749c9d64041de66e34ad8e70 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 1012896f4225e8f801ff3c1648023845b66dfb11 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 775b4dc9618a99a1fa48b57554041a5dc17e1336 git Not specified
CNA Linux Linux affected 8b6a361b8c482f22ac99c3273285ff16b23fba91 0ce1bc9e46ecabe84772bb561e373c0d9876d6f2 git Not specified
CNA Linux Linux affected 5.3 Not specified
CNA Linux Linux unaffected 5.3 semver Not specified
CNA Linux Linux unaffected 5.10.258 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.209 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.175 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.142 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.92 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.34 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.11 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/683f7cfbf514193d63c0efa079f3352bde84c2e0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/775b4dc9618a99a1fa48b57554041a5dc17e1336 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c7c0c0f4379dedec12d24dbb9dded5d2db7fd9f2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/14553be882d9ce91749c9d64041de66e34ad8e70 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1012896f4225e8f801ff3c1648023845b66dfb11 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/33a8b5e971e294ec2a7b74211c545e09efd8e9ac 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/4a331582011d9e8089af8aa2a61ec6b4443bb245 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0ce1bc9e46ecabe84772bb561e373c0d9876d6f2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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