{"id":"CVE-2026-89533","summary":"svcrdma: Fix offset arithmetic in read_chunk_range","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nsvcrdma: Fix offset arithmetic in read_chunk_range\n\nsvc_rdma_read_chunk_range() walks a Read chunk's segment list to\nbuild a sub-range starting at byte offset and spanning length bytes\nfor a Position-Zero or Call chunk. Two arithmetic defects in the\nper-segment loop produce wrong DMA lengths and a u32 underflow:\n\n    pcl_for_each_segment(segment, chunk) {\n            if (offset \u003e segment-\u003ers_length) {\n                    offset -= segment-\u003ers_length;\n                    continue;\n            }\n\n            dummy.rs_handle = segment-\u003ers_handle;\n            dummy.rs_length = min_t(u32, length,\n                                    segment-\u003ers_length) - offset;\n            dummy.rs_offset = segment-\u003ers_offset + offset;\n\nFirst, the skip predicate uses '\u003e' instead of '\u003e='. When offset\nequals the segment's full rs_length, the segment is fully consumed\nand should be skipped, but the loop falls through into the body.\nThe resulting dummy.rs_length is min_t(u32, length, rs_length) -\nrs_length, which underflows to a near-UINT_MAX u32 when length is\nsmaller than rs_length, or is zero otherwise.\n\nSecond, the length formula subtracts offset from the min_t() result\nrather than from segment-\u003ers_length before the cap. For offset \u003e 0\nthe segment's residual is rs_length - offset, not rs_length, so the\ncap must be applied to the residual. With the current bracketing,\nwhenever length is smaller than rs_length - offset the per-segment\nlength becomes length - offset instead of length, silently dropping\noffset bytes from the rebuilt chunk. Combined with the boundary\ncase above it also enables the u32 underflow path, which propagates\na huge nr_bvec into svc_rdma_build_read_segment() and a multi-MiB\nkmalloc_array_node() in svc_rdma_get_rw_ctxt().\n\nAdditionally, svc_rdma_read_call_chunk() can invoke this function\nwith length == 0 when the last Read chunk ends exactly at the end\nof the Call chunk. With the corrected \u003e= predicate, every segment\nis skipped and the function returns the initial -EINVAL, rejecting\na valid request. Return success immediately when length is zero.\nAlso break out of the loop once length is fully consumed to avoid\npassing zero-length segments to svc_rdma_build_read_segment().\n\nFix by using '\u003e=' so a fully-consumed segment is skipped, by\nmoving '- offset' inside min_t() so the cap is applied to the\nsegment's residual length, by returning success for zero-length\nrequests, and by stopping iteration when the requested range has\nbeen consumed.","modified":"2026-09-13T03:47:19.156438215Z","published":"2026-09-11T19:44:12.236Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89533.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/4493c96bbd0068fadf69cbae8d13426202e34cdc"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/6ee4dc7476b3abc92ec1d444533a559f33f59561"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a46b35f213c2426f5d6a0458a8f7e873fc59cdfd"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89533.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89533"},{"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":"d7cc73972661be4a02a1b09f1d9b3283c6c05154"},{"fixed":"6ee4dc7476b3abc92ec1d444533a559f33f59561"},{"fixed":"a46b35f213c2426f5d6a0458a8f7e873fc59cdfd"},{"fixed":"4493c96bbd0068fadf69cbae8d13426202e34cdc"},{"fixed":"4a44c140cc2f3643a39e258bb0c0ab9d0f494f5e"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89533.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"6.12.109"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.50"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.2.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89533.json"}}],"schema_version":"1.9.0"}