Re: [PATCH v1] perf trace: Fix runtime error of index out of bounds

[Namhyung Kim <namhyung@kernel.org>]

On Tue, Jan 21, 2025 at 06:55:19PM -0800, Howard Chu wrote:
> libtraceevent parses and returns an array of argument fields, sometimes
> larger than RAW_SYSCALL_ARGS_NUM (6) because it includes "__syscall_nr",
> idx will traverse to index 6 (7th element) whereas sc->fmt->arg holds 6
> elements max, creating an out-of-bounds access. This runtime error is
> found by UBsan. The error message:

I'm curious how I miss this.  Is this only for some specific syscalls or
always happening?  Do you which commit introduced this?

Thanks,
Namhyung

> 
> perf $ sudo UBSAN_OPTIONS=print_stacktrace=1 ./perf trace -a --max-events=1
> builtin-trace.c:1966:35: runtime error: index 6 out of bounds for type 'syscall_arg_fmt [6]'
>     #0 0x5c04956be5fe in syscall__alloc_arg_fmts /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:1966
>     #1 0x5c04956c0510 in trace__read_syscall_info /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:2110
>     #2 0x5c04956c372b in trace__syscall_info /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:2436
>     #3 0x5c04956d2f39 in trace__init_syscalls_bpf_prog_array_maps /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:3897
>     #4 0x5c04956d6d25 in trace__run /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:4335
>     #5 0x5c04956e112e in cmd_trace /home/howard/hw/linux-perf/tools/perf/builtin-trace.c:5502
>     #6 0x5c04956eda7d in run_builtin /home/howard/hw/linux-perf/tools/perf/perf.c:351
>     #7 0x5c04956ee0a8 in handle_internal_command /home/howard/hw/linux-perf/tools/perf/perf.c:404
>     #8 0x5c04956ee37f in run_argv /home/howard/hw/linux-perf/tools/perf/perf.c:448
>     #9 0x5c04956ee8e9 in main /home/howard/hw/linux-perf/tools/perf/perf.c:556
>     #10 0x79eb3622a3b7 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
>     #11 0x79eb3622a47a in __libc_start_main_impl ../csu/libc-start.c:360
>     #12 0x5c04955422d4 in _start (/home/howard/hw/linux-perf/tools/perf/perf+0x4e02d4) (BuildId: 5b6cab2d59e96a4341741765ad6914a4d784dbc6)
> 
>      0.000 ( 0.014 ms): Chrome_ChildIO/117244 write(fd: 238, buf: !, count: 1)                                      = 1
> 
> Signed-off-by: Howard Chu <howardchu95@gmail.com>
> ---
>  tools/perf/builtin-trace.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> index d7c7d29291fb..8d3260bad10a 100644
> --- a/tools/perf/builtin-trace.c
> +++ b/tools/perf/builtin-trace.c
> @@ -2108,7 +2108,7 @@ static int trace__read_syscall_info(struct trace *trace, int id)
>  	}
>  
>  	if (syscall__alloc_arg_fmts(sc, IS_ERR(sc->tp_format) ?
> -					RAW_SYSCALL_ARGS_NUM : sc->tp_format->format.nr_fields))
> +					RAW_SYSCALL_ARGS_NUM : sc->tp_format->format.nr_fields - 1))
>  		return -ENOMEM;
>  
>  	sc->args = sc->tp_format->format.fields;
> -- 
> 2.45.2
>