{"id":"CVE-2026-89532","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-\u003ech_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-\u003ers_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-\u003ech_list, &pcl-\u003ecl_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 \u003c= &ch_segments[0u - 1u]  /* 0xFFFFFFFF */\n          segment-\u003ers_handle            /* OOB read -\u003e 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 \u003e 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.","modified":"2026-09-13T03:47:19.045101039Z","published":"2026-09-11T19:44:11.495Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89532.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/6d33a7e6bf6c6b293a266a617201285a1ad32c56"},{"type":"WEB","url":"https://git.kernel.org/stable/c/9c5a03c3dc505c0295339b0a1b9e4fe36447e482"},{"type":"WEB","url":"https://git.kernel.org/stable/c/a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b7713a784c59515d0aba558c8f5df6a0164dd3a9"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89532.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89532"},{"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":"78147ca8b4a9b6cf0e597ddd6bf17959e08376c2"},{"fixed":"9c5a03c3dc505c0295339b0a1b9e4fe36447e482"},{"fixed":"a1c954ca4977a4e6ec73ef92fe48073ec54f9fc8"},{"fixed":"6d33a7e6bf6c6b293a266a617201285a1ad32c56"},{"fixed":"b7713a784c59515d0aba558c8f5df6a0164dd3a9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89532.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-2026-89532.json"}}],"schema_version":"1.9.0"}