CVE-2026-99163

In the Linux kernel, the following vulnerability has been resolved:

tracing/histograms: Reject non-stacktrace fields for synthetic stacktrace fields

In check_synth_field(), when a synthetic event field is a stacktrace (field->is_stack) and the histogram field is not a long[ stacktrace array, validation falls through to the generic size and signedness comparison.

Because parse_synth_field() sets a stacktrace fields type to __data_loc unsigned long[], its size is sizeof(u64) and synth_field_signed() marks it as signed. Consequently, any 8-byte signed scalar histogram field passes the fallback check, and its scalar value is subsequently dereferenced as a kernel stacktrace pointer in get_field_size() and trace_stack().

Furthermore, checking strstr(hist_field->type, long[) is insufficient because tracepoint fields defined with __bitmask() or __rel_bitmask() also have type __data_loc unsigned long[] or __rel_loc unsigned long[], whilst create_hist_field() treats them as 4-byte scalar values without HIST_FIELD_FL_STACKTRACE.

Propagate HIST_FIELD_FL_STACKTRACE to variable references and field variables (whilst excluding variable aliases from per-element stacktrace capture), and reject any mismatch between HIST_FIELD_FL_STACKTRACE and field->is_stack in check_synth_field().

Affected Software

References

• https://git.kernel.org/stable/c/1f36e4ddd05d540f363dbaa4c23042549f15b3ef
• https://git.kernel.org/stable/c/326c45c9e201e3ff4c9e9e0e14c2c91364d6c8be
• https://git.kernel.org/stable/c/648687f2b448d8527cd7b112fe5d4bd0fec85a87
• https://git.kernel.org/stable/c/6c4e4946febb585d2fc93a02a0cd12cec715bb32
• https://git.kernel.org/stable/c/7e0d05a6234a984ac23b8a563fb7f66f2572b668
• https://git.kernel.org/stable/c/a244c241593b5b38a08f0df2cb43c26574efbdcb
• https://git.kernel.org/stable/c/deb336ae7c7b341591a6862cf6fcfeca97c77dfd
• https://git.kernel.org/stable/c/eba0a6365a0f38f7598a02fc7f9ee341c7efe7f5