ring-buffer: Fix event length with forced 8-byte alignment

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80876
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-04 17:16:59 UTC
Updated2026-09-04 17:16:59 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ring-buffer: Fix event length with forced 8-byte alignment When RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length() reserves the space of event->array[0] for placing the data length and rb_update_event() stores the data length in event->array[0] accordingly. As a result the whole event length will add extra 4 bytes for sizeof(event.array[0]) unconditionally. But ring_buffer_event_length() only subtracts the sizeof(event->array[0]) for events larger than RB_MAX_SMALL_DATA + sizeof(event->array[0]). As a result, small events on architectures with RB_FORCE_8BYTE_ALIGNMENT=true report a data length that is 4 bytes larger than expected. To fix it, add the RB_FORCE_8BYTE_ALIGNMENT as a condition to subtract the size of that length field whenever RB_FORCE_8BYTE_ALIGNMENT is true. This issue is observed in a riscv64 kernel with CONFIG_HAVE_64BIT_ALIGNED_ACCESS set to y, when we run ftrace selftest trace_marker_raw.tc, we get the weird log: for cases where the id is 1..100, the number of data field is 8*N, but once id exceeds 100, the number of data field becomes 8*N+4: # 1 buf: 58 00 00 00 80 5e d1 63 (number of data field is 8*1) ... # a buf: 58 ... (number of data field is 8*2) ... # 64 buf: 58 ... (number of data field is 8*13) # 65 buf: 58 ... (number of data field is 8*13+4) After applying this change, the number of data field keeps being 8*N+4 consistently.

Risk And Classification

EPSS: 0.001640000 probability, percentile 0.059220000 (date 2026-09-07)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 7c9f0ccf9f04142458d2ac3d39414f4acae242f0 git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 24c3fa71f9947b0e1f3b954db1b769b44140192e git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 14057268e79654c3e8ea2c9b5204cb9644b2964d git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 dbcb8635b1eb7603818591cf745c7b1d714f7ac6 git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 cfada73fabe2ccc06ec77fe2ceaa088689213326 git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 ec5e96aee75d27779b9a860307679f13f33adb0c git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992 git Not specified
CNA Linux Linux affected 2271048d1b3b0aabf83d25b29c20646dcabedc05 c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0 git Not specified
CNA Linux Linux affected 2.6.34 Not specified
CNA Linux Linux unaffected 2.6.34 semver Not specified
CNA Linux Linux unaffected 5.10.261 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.212 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7c9f0ccf9f04142458d2ac3d39414f4acae242f0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cfada73fabe2ccc06ec77fe2ceaa088689213326 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/ec5e96aee75d27779b9a860307679f13f33adb0c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/14057268e79654c3e8ea2c9b5204cb9644b2964d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dbcb8635b1eb7603818591cf745c7b1d714f7ac6 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/24c3fa71f9947b0e1f3b954db1b769b44140192e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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