On Tue, 25 Jan 2022 14:00:37 -0800
Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> As done for trace_events.h, also fix the __rel_loc macro in perf.h,
> which silences the -Warray-bounds warning:
>
> In file included from ./include/linux/string.h:253,
> from ./include/linux/bitmap.h:11,
> from ./include/linux/cpumask.h:12,
> from ./include/linux/mm_types_task.h:14,
> from ./include/linux/mm_types.h:5,
> from ./include/linux/buildid.h:5,
> from ./include/linux/module.h:14,
> from samples/trace_events/trace-events-sample.c:2:
> In function '__fortify_strcpy',
> inlined from 'perf_trace_foo_rel_loc' at samples/trace_events/./trace-events-sample.h:519:1:
> ./include/linux/fortify-string.h:47:33: warning: '__builtin_strcpy' offset 12 is out of the bounds [
> 0, 4] [-Warray-bounds]
> 47 | #define __underlying_strcpy __builtin_strcpy
> | ^
> ./include/linux/fortify-string.h:445:24: note: in expansion of macro '__underlying_strcpy'
> 445 | return __underlying_strcpy(p, q);
> | ^~~~~~~~~~~~~~~~~~~
>
> Also make __data struct member a proper flexible array to avoid future
> problems.
>
This looks good to me.
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
BTW, same macro is in the include/trace/bpf_probe.h.
I'm not sure bpf using this macro, should we update it for
consistency?
> Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> include/trace/perf.h | 5 +++--
> include/trace/trace_events.h | 2 +-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/trace/perf.h b/include/trace/perf.h
> index b77d09c70a93..5800d13146c3 100644
> --- a/include/trace/perf.h
> +++ b/include/trace/perf.h
> @@ -26,8 +26,9 @@
>
> #undef __get_rel_dynamic_array
> #define __get_rel_dynamic_array(field) \
> - ((void *)(&__entry->__rel_loc_##field) + \
> - sizeof(__entry->__rel_loc_##field) + \
> + ((void *)__entry + \
> + offsetof(typeof(*__entry), __rel_loc_##field) + \
> + sizeof(__entry->__rel_loc_##field) + \
> (__entry->__rel_loc_##field & 0xffff))
>
> #undef __get_rel_dynamic_array_len
> diff --git a/include/trace/trace_events.h b/include/trace/trace_events.h
> index cefefed18e85..7c86cc541c7a 100644
> --- a/include/trace/trace_events.h
> +++ b/include/trace/trace_events.h
> @@ -134,7 +134,7 @@ TRACE_MAKE_SYSTEM_STR();
> struct trace_event_raw_##name { \
> struct trace_entry ent; \
> tstruct \
> - char __data[0]; \
> + char __data[]; \
> }; \
> \
> static struct trace_event_class event_class_##name;
> --
> 2.30.2
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
