In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ring-buffer: Fix event length with forced 8-byte alignment<\/p>\n
When 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.<\/p>\n
But 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.<\/p>\n
To 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.<\/p>\n
This 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)<\/p>\n
After applying this change, the number of data field keeps being 8*N+4
\nconsistently.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ring-buffer: Fix event length with forced 8-byte alignment<\/p>\n
When RB_FORCE_8BYTE_ALIGNMENT is true, rb_calculate_event_length()
\nrese<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-17424","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/17424","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=17424"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=17424"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=17424"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}