GHSA-FFXC-RC5X-R6RP
Vulnerability from github – Published: 2026-07-25 12:31 – Updated: 2026-08-23 15:32In the Linux kernel, the following vulnerability has been resolved:
RDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg
When the server answers an RTRS READ, rdma_write_sg() builds the source scatter/gather entry for the IB_WR_RDMA_WRITE that returns data to the peer. Its length is taken directly from the wire descriptor:
plist->length = le32_to_cpu(id->rd_msg->desc[0].len);
rd_msg points into the chunk buffer that the remote peer filled via RDMA-WRITE-WITH-IMM (rtrs_srv_rdma_done() -> process_io_req() -> process_read()), so desc[0].len is attacker-controlled and, before this change, was only rejected when zero. The source address is the fixed chunk start (dma_addr[msg_id]) and the source lkey is the PD-wide local_dma_lkey, which is not tied to the chunk's MR mapping, so the verbs layer does not constrain the transfer length to max_chunk_size. msg_id and off are bounded against queue_depth and max_chunk_size in rtrs_srv_rdma_done(), but desc[0].len is a separate field that was not checked against the chunk size.
A peer that advertises desc[0].len larger than max_chunk_size can make the posted RDMA write read past the chunk's mapped region. The resulting behaviour depends on the IOMMU configuration: with no IOMMU or in passthrough mode the read may extend into memory adjacent to the chunk and be returned to the peer, which can disclose host memory; with a translating IOMMU the out-of-range access is expected to fault and abort the connection. In either case the transfer exceeds what the protocol permits and is driven by a remote peer.
Reject a descriptor length above max_chunk_size, mirroring the existing off >= max_chunk_size bound in rtrs_srv_rdma_done(). Legitimate clients do not exceed it: the client sets desc[0].len to its MR length, which is capped at the negotiated max_io_size (max_chunk_size - MAX_HDR_SIZE).
{
"affected": [],
"aliases": [
"CVE-2026-64269"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-25T10:17:07Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/rtrs-srv: Bound RDMA-Write length to chunk size in rdma_write_sg\n\nWhen the server answers an RTRS READ, rdma_write_sg() builds the source\nscatter/gather entry for the IB_WR_RDMA_WRITE that returns data to the\npeer. Its length is taken directly from the wire descriptor:\n\n plist-\u003elength = le32_to_cpu(id-\u003erd_msg-\u003edesc[0].len);\n\nrd_msg points into the chunk buffer that the remote peer filled via\nRDMA-WRITE-WITH-IMM (rtrs_srv_rdma_done() -\u003e process_io_req() -\u003e\nprocess_read()), so desc[0].len is attacker-controlled and, before this\nchange, was only rejected when zero. The source address is the fixed\nchunk start (dma_addr[msg_id]) and the source lkey is the PD-wide\nlocal_dma_lkey, which is not tied to the chunk\u0027s MR mapping, so the verbs\nlayer does not constrain the transfer length to max_chunk_size. msg_id\nand off are bounded against queue_depth and max_chunk_size in\nrtrs_srv_rdma_done(), but desc[0].len is a separate field that was not\nchecked against the chunk size.\n\nA peer that advertises desc[0].len larger than max_chunk_size can make\nthe posted RDMA write read past the chunk\u0027s mapped region. The resulting\nbehaviour depends on the IOMMU configuration: with no IOMMU or in\npassthrough mode the read may extend into memory adjacent to the chunk\nand be returned to the peer, which can disclose host memory; with a\ntranslating IOMMU the out-of-range access is expected to fault and abort\nthe connection. In either case the transfer exceeds what the protocol\npermits and is driven by a remote peer.\n\nReject a descriptor length above max_chunk_size, mirroring the existing\noff \u003e= max_chunk_size bound in rtrs_srv_rdma_done(). Legitimate clients\ndo not exceed it: the client sets desc[0].len to its MR length, which is\ncapped at the negotiated max_io_size (max_chunk_size - MAX_HDR_SIZE).",
"id": "GHSA-ffxc-rc5x-r6rp",
"modified": "2026-08-23T15:32:55Z",
"published": "2026-07-25T12:31:28Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64269"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2912f3d40355dabc08fdbaaf2764d02445fe88dc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5a45d0aa1fa50a333ce5763ade744e2d89838667"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/68c09762172f6224e9ddf9b0a60bacbb36e443eb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6cada540150894e81042a0ae0c796a21a9a877da"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6f40246f4312fdbab5a13cc440adebf95eb2aa66"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/963af8d97a8c6a117134a8d0db1415e0489200b1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a35b7a8728a53ddc80b323970689fa5985816836"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/da3e44add94b05dfde56f898421922f5cf35705f"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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