{"id":"CVE-2026-80876","summary":"ring-buffer: Fix event length with forced 8-byte alignment","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Fix event length with forced 8-byte alignment\n\nWhen RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()\nreserves the space of event-\u003earray[0] for placing the data length and\nrb_update_event() stores the data length in event-\u003earray[0]\naccordingly. As a result the whole event length will add extra 4 bytes\nfor sizeof(event.array[0]) unconditionally.\n\nBut ring_buffer_event_length() only subtracts the\nsizeof(event-\u003earray[0]) for events larger than RB_MAX_SMALL_DATA +\nsizeof(event-\u003earray[0]). As a result, small events on architectures\nwith RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4\nbytes larger than expected.\n\nTo fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract\nthe size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is\ntrue.\n\nThis issue is observed in a riscv64 kernel with\nCONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest\ntrace_marker_raw.tc, we get the weird log: for cases where the id is\n1..100, the number of data field is 8*N, but once id exceeds 100, the\nnumber of data field becomes 8*N+4:\n # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1)\n ...\n # a buf: 58 ...                  (number of data field is 8*2)\n ...\n # 64 buf: 58 ...                 (number of data field is 8*13)\n # 65 buf: 58 ...                 (number of data field is 8*13+4)\n\nAfter applying this change, the number of data field keeps being 8*N+4\nconsistently.","modified":"2026-09-06T03:47:01.427273799Z","published":"2026-09-04T16:48:50.082Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80876.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326"},{"type":"WEB","url":"https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/80xxx/CVE-2026-80876.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-80876"},{"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":"2271048d1b3b0aabf83d25b29c20646dcabedc05"},{"fixed":"7c9f0ccf9f04142458d2ac3d39414f4acae242f0"},{"fixed":"24c3fa71f9947b0e1f3b954db1b769b44140192e"},{"fixed":"14057268e79654c3e8ea2c9b5204cb9644b2964d"},{"fixed":"dbcb8635b1eb7603818591cf745c7b1d714f7ac6"},{"fixed":"cfada73fabe2ccc06ec77fe2ceaa088689213326"},{"fixed":"ec5e96aee75d27779b9a860307679f13f33adb0c"},{"fixed":"3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992"},{"fixed":"c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80876.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.6.34"},{"fixed":"5.10.261"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.212"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.97"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.40"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.5"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-80876.json"}}],"schema_version":"1.9.0"}