CVE-2026-80876 is a vulnerability in Linux Kernel
Published on September 4, 2026
ring-buffer: Fix event length with forced 8-byte alignment
In 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.
Products Associated with CVE-2026-80876
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Affected Versions
Linux:- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below 7c9f0ccf9f04142458d2ac3d39414f4acae242f0 is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below 24c3fa71f9947b0e1f3b954db1b769b44140192e is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below 14057268e79654c3e8ea2c9b5204cb9644b2964d is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below dbcb8635b1eb7603818591cf745c7b1d714f7ac6 is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below cfada73fabe2ccc06ec77fe2ceaa088689213326 is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below ec5e96aee75d27779b9a860307679f13f33adb0c is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below 3a63a11897c7ba32d1be7a3fdbc48a8b01cf4992 is affected.
- Version 2271048d1b3b0aabf83d25b29c20646dcabedc05 and below c37e0a4b79a6bbb96ce5ffe279d7c001e20529e0 is affected.
- Version 2.6.34 is affected.
- Before 2.6.34 is unaffected.
- Version 5.10.261, <= 5.10.* is unaffected.
- Version 5.15.212, <= 5.15.* is unaffected.
- Version 6.1.178, <= 6.1.* is unaffected.
- Version 6.6.145, <= 6.6.* is unaffected.
- Version 6.12.97, <= 6.12.* is unaffected.
- Version 6.18.40, <= 6.18.* is unaffected.
- Version 7.1.5, <= 7.1.* is unaffected.
- Version 7.2, <= * is unaffected.