{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-89532", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-89532" ], "published": "2026-09-11T19:47:07Z", "summary": "svcrdma: Fix pcl_for_each_segment for empty chunks", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nsvcrdma: Fix pcl_for_each_segment for empty chunks\n\nWhen a parsed chunk list contains a chunk whose ch_segcount is zero,\npcl_for_each_segment computes its inclusive upper bound as\n&chunk->ch_segments[ch_segcount - 1]. ch_segcount is u32, so the\nsubtraction wraps to 0xFFFFFFFF and the bound lands far past the\nch_segments flex array. The loop body then walks unrelated memory at\nsizeof(struct svc_rdma_segment) stride until it faults.\n\nA zero-segcount chunk is reachable from the wire:\nxdr_check_write_chunk() only rejects segcount values greater than\nrc_maxpages, and pcl_alloc_write() links a freshly allocated chunk\nonto rc_write_pcl/rc_reply_pcl before its segment-fill loop runs,\nso a Write or Reply chunk advertising zero segments leaves\nch_segcount == 0 on the list. When the transport has negotiated\nSend-With-Invalidate, svc_rdma_get_inv_rkey() iterates all four\nPCLs with pcl_for_each_segment and dereferences segment->rs_handle\non each iteration, turning the underflow into an out-of-bounds read\nand a general protection fault.\n\n xdr_check_write_list / xdr_check_reply_chunk\n pcl_alloc_write()\n chunk = pcl_alloc_chunk(...) /* ch_segcount = 0 */\n list_add_tail(&chunk->ch_list, &pcl->cl_chunks)\n /* fill loop iterates zero times for wire segcount 0 */\n\n svc_rdma_get_inv_rkey()\n pcl_for_each_chunk(rc_write_pcl)\n pcl_for_each_segment(segment, chunk)\n pos <= &ch_segments[0u - 1u] /* 0xFFFFFFFF */\n segment->rs_handle /* OOB read -> GPF */\n\nFix by switching the macro to a half-open upper bound that uses\nch_segcount directly. For ch_segcount == 0 the loop start equals the\nloop end and the body is skipped; for ch_segcount > 0 the iteration\nrange is unchanged. All six existing call sites in\nnet/sunrpc/xprtrdma/svc_rdma_recvfrom.c and\nnet/sunrpc/xprtrdma/svc_rdma_rw.c remain correct under the new bound,\nso no caller changes are needed.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.47-1+rpt4" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi3-rpi-2712", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v6", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l", "binary_version": "1:6.1.47-1+rpt4" }, { "binary_name": "linux-image-6.1.0-rpi3-rpi-v8", "binary_version": "1:6.1.47-1+rpt4" } ] }, "database_specific": { "per_version": { "1:6.1.47-1+rpt4": { "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e", "upstream_version": "6.1.47", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.1.188", "compiled_filter": false } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-89532" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/1e2e3481e39103a386b86be1c33eaef97cbdf16e" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/3a78b841879c2a3243f74edc514236fb2907167f" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/06d0390c37fa6714624af771bd72bbf1a7ed9bb1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/9c5a03c3dc505c0295339b0a1b9e4fe36447e482" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/6d33a7e6bf6c6b293a266a617201285a1ad32c56" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b7713a784c59515d0aba558c8f5df6a0164dd3a9" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-09-14T12:06:03Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 9.1, "cvss_v3_severity": "Critical", "scenario": "AV:N - svcrdma is the nfsd RPC-over-RDMA server transport and parses Write/Reply chunks from remote peers over iWARP or routable RoCEv2; a remote NFS/RDMA client triggers the bug with a crafted transport header on an established RDMA connection.\nAC:L - The attacker sets RPCRDMA_CMP_F_SND_W_INV_OK on connect and sends a Write or Reply chunk with segcount 0, which xdr_check_write_chunk accepts; Send-With-Invalidate is available on typical RDMA devices, so svc_rdma_get_inv_rkey hits the underflow deterministically.\nPR:N - svc_rdma_xdr_decode_req and svc_rdma_get_inv_rkey run in svc_rdma_recvfrom before svc_process/svc_authenticate; RDMA CM accept and RPC-over-RDMA header parsing require no NFS credentials or capabilities.\nUI:N - Exploitation requires only attacker-generated RDMA connect and RPC-over-RDMA messages to a listening NFS/RDMA service; no victim user action is needed.\nS:U - The out-of-bounds read and resulting general protection fault occur in the host kernel NFS/RDMA server and do not cross a VM, IOMMU, or sandbox boundary.\nC:H - With ch_segcount 0, pcl_for_each_segment underflows the u32 bound to 0xFFFFFFFF and walks adjacent kernel heap at sizeof(struct svc_rdma_segment) stride, an unbounded out-of-bounds read rather than a few-byte leak.\nI:N - svc_rdma_get_inv_rkey only loads segment->rs_handle from the overrun pointer; the defect is a read-only walk with no out-of-bounds write, use-after-free, or control-flow hijack primitive.\nA:H - The unbounded walk continues until it hits unmapped memory and raises a general protection fault, oopsing or panicking the kernel, and the attacker can repeat it on each request." } } }