{"id":"CVE-2026-80876","state":"PUBLISHED","title":"ring-buffer: Fix event length with forced 8-byte alignment","description":"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->array[0] for placing the data length and\nrb_update_event() stores the data length in event->array[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->array[0]) for events larger than RB_MAX_SMALL_DATA +\nsizeof(event->array[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.","publishedAt":"2026-09-04T16:48:50.082Z","updatedAt":"2026-09-04T16:48:50.082Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"7c9f0ccf9f04142458d2ac3d39414f4acae242f0","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"24c3fa71f9947b0e1f3b954db1b769b44140192e","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"14057268e79654c3e8ea2c9b5204cb9644b2964d","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"dbcb8635b1eb7603818591cf745c7b1d714f7ac6","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"cfada73fabe2ccc06ec77fe2ceaa088689213326","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"ec5e96aee75d27779b9a860307679f13f33adb0c","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.34","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.34","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]}],"references":["https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0","https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e","https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d","https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6","https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326","https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c","https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992","https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:07.220Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/80xxx/CVE-2026-80876.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-80876","state":"PUBLISHED","datePublished":"2026-09-04T16:48:50.082Z","dateUpdated":"2026-09-04T16:48:50.082Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-26T14:34:25.799Z"},"containers":{"cna":{"title":"ring-buffer: Fix event length with forced 8-byte alignment","descriptions":[{"lang":"en","value":"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->array[0] for placing the data length and\nrb_update_event() stores the data length in event->array[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->array[0]) for events larger than RB_MAX_SMALL_DATA +\nsizeof(event->array[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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"7c9f0ccf9f04142458d2ac3d39414f4acae242f0","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"24c3fa71f9947b0e1f3b954db1b769b44140192e","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"14057268e79654c3e8ea2c9b5204cb9644b2964d","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"dbcb8635b1eb7603818591cf745c7b1d714f7ac6","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"cfada73fabe2ccc06ec77fe2ceaa088689213326","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"ec5e96aee75d27779b9a860307679f13f33adb0c","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992","versionType":"git"},{"version":"2271048d1b3b0aabf83d25b29c20646dcabedc05","status":"affected","lessThan":"c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.34","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.34","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.212","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.97","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0"},{"url":"https://git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e"},{"url":"https://git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d"},{"url":"https://git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6"},{"url":"https://git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326"},{"url":"https://git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c"},{"url":"https://git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992"},{"url":"https://git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-09-04T16:48:50.082Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"5.15.212"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"6.12.97"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.34","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}