--- id: CVE-2026-89533 title: 'svcrdma: Fix offset arithmetic in read_chunk_range' summary: |- In the Linux kernel, the following vulnerability has been resolved: svcrdma: Fix offset arithmetic in read_chunk_range svc_rdma_read_chunk_range() walks a Read chunk's segment list to build a sub-range starting at byte offset and spann… severity: critical cvss: 9.8 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cvssSource: cna cwe: - CWE-191 vendor: Linux product: Linux affected: - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 10873311f91db9454e2fadbf9866bc819e0646d9 - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7 - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < cba8543c18cf42fd80fd63effb6df6ff4f7e73ce - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 6ee4dc7476b3abc92ec1d444533a559f33f59561 - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < a46b35f213c2426f5d6a0458a8f7e873fc59cdfd - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 4493c96bbd0068fadf69cbae8d13426202e34cdc - >- Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e - Linux 5.11 ssvc: exploitation: none automatable: 'yes' technicalImpact: total timestamp: '2026-10-16T19:23:13.656876Z' published: '2026-09-11' updated: '2026-10-19' sourceUpdated: '2026-10-19T08:48:24.875Z' source: CVEORG sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89533' references: - url: 'https://git.kernel.org/stable/c/10873311f91db9454e2fadbf9866bc819e0646d9' - url: 'https://git.kernel.org/stable/c/addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7' - url: 'https://git.kernel.org/stable/c/cba8543c18cf42fd80fd63effb6df6ff4f7e73ce' - url: 'https://git.kernel.org/stable/c/6ee4dc7476b3abc92ec1d444533a559f33f59561' - url: 'https://git.kernel.org/stable/c/a46b35f213c2426f5d6a0458a8f7e873fc59cdfd' - url: 'https://git.kernel.org/stable/c/4493c96bbd0068fadf69cbae8d13426202e34cdc' - url: 'https://git.kernel.org/stable/c/4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e' - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89533.json - url: 'https://access.redhat.com/security/cve/CVE-2026-89533' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532058' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89533' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89533' - url: >- https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89533.mbox tags: - cve.org - csaf - vex - red-hat - score-dispute epss: 0.00502 epssPercentile: 0.42784 scores: cna: 9.8 vendor: 7 ingestedAt: '2026-09-14T15:23:07.452Z' --- ## Overview In the Linux kernel, the following vulnerability has been resolved: svcrdma: Fix offset arithmetic in read_chunk_range svc_rdma_read_chunk_range() walks a Read chunk's segment list to build a sub-range starting at byte offset and spanning length bytes for a Position-Zero or Call chunk. Two arithmetic defects in the per-segment loop produce wrong DMA lengths and a u32 underflow: pcl_for_each_segment(segment, chunk) { if (offset > segment->rs_length) { offset -= segment->rs_length; continue; } dummy.rs_handle = segment->rs_handle; dummy.rs_length = min_t(u32, length, segment->rs_length) - offset; dummy.rs_offset = segment->rs_offset + offset; First, the skip predicate uses '>' instead of '>='. When offset equals the segment's full rs_length, the segment is fully consumed and should be skipped, but the loop falls through into the body. The resulting dummy.rs_length is min_t(u32, length, rs_length) - rs_length, which underflows to a near-UINT_MAX u32 when length is smaller than rs_length, or is zero otherwise. Second, the length formula subtracts offset from the min_t() result rather than from segment->rs_length before the cap. For offset > 0 the segment's residual is rs_length - offset, not rs_length, so the cap must be applied to the residual. With the current bracketing, whenever length is smaller than rs_length - offset the per-segment length becomes length - offset instead of length, silently dropping offset bytes from the rebuilt chunk. Combined with the boundary case above it also enables the u32 underflow path, which propagates a huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB kmalloc_array_node() in svc_rdma_get_rw_ctxt(). Additionally, svc_rdma_read_call_chunk() can invoke this function with length == 0 when the last Read chunk ends exactly at the end of the Call chunk. With the corrected >= predicate, every segment is skipped and the function returns the initial -EINVAL, rejecting a valid request. Return success immediately when length is zero. Also break out of the loop once length is fully consumed to avoid passing zero-length segments to svc_rdma_build_read_segment(). Fix by using '>=' so a fully-consumed segment is skipped, by moving '- offset' inside min_t() so the cap is applied to the segment's residual length, by returning success for zero-length requests, and by stopping iteration when the requested range has been consumed. ## Affected - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 10873311f91db9454e2fadbf9866bc819e0646d9` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < addbf02dfe3b25e7e38e03bbd4e2a6ed86a14be7` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < cba8543c18cf42fd80fd63effb6df6ff4f7e73ce` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 6ee4dc7476b3abc92ec1d444533a559f33f59561` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < a46b35f213c2426f5d6a0458a8f7e873fc59cdfd` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 4493c96bbd0068fadf69cbae8d13426202e34cdc` - `Linux >= d7cc73972661be4a02a1b09f1d9b3283c6c05154 < 4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e` - `Linux 5.11` ## Remediation Refer to the linked advisories for vendor-supplied fixes and affected version ranges. ## Vendor advisories - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-14 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89533.json)