linux-kernel - Re: [PATCH v2 1/5] perf disasm: Avoid undefined behavior in incrementing NULL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <87h5y09u5l.fsf@gmail.com>
Date: Thu, 21 Aug 2025 15:39:18 -0700
From: Collin Funk <collin.funk1@...il.com>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>,  Ingo Molnar <mingo@...hat.com>,
  Arnaldo Carvalho de Melo <acme@...nel.org>,  Namhyung Kim
 <namhyung@...nel.org>,  Mark Rutland <mark.rutland@....com>,  Alexander
 Shishkin <alexander.shishkin@...ux.intel.com>,  Jiri Olsa
 <jolsa@...nel.org>,  Adrian Hunter <adrian.hunter@...el.com>,  Kan Liang
 <kan.liang@...ux.intel.com>,  Chun-Tse Shao <ctshao@...gle.com>,  Blake
 Jones <blakejones@...gle.com>,  James Clark <james.clark@...aro.org>,  Jan
 Polensky <japo@...ux.ibm.com>,  Howard Chu <howardchu95@...il.com>,
  Thomas Gleixner <tglx@...utronix.de>,  Nam Cao <namcao@...utronix.de>,
  Li Huafei <lihuafei1@...wei.com>,  "Steinar H. Gunderson"
 <sesse@...gle.com>,  Athira Rajeev <atrajeev@...ux.ibm.com>,
  linux-perf-users@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] perf disasm: Avoid undefined behavior in
 incrementing NULL

Ian Rogers <irogers@...gle.com> writes:

> Incrementing NULL is undefined behavior and triggers ubsan during the
> perf annotate test. Split a compound statement over two lines to avoid
> this.
>
> Fixes: 98f69a573c66 ("perf annotate: Split out util/disasm.c")
> Signed-off-by: Ian Rogers <irogers@...gle.com>
> Acked-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/util/disasm.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
> index b1e4919d016f..e257bd918c89 100644
> --- a/tools/perf/util/disasm.c
> +++ b/tools/perf/util/disasm.c
> @@ -390,13 +390,16 @@ static int jump__parse(struct arch *arch, struct ins_operands *ops, struct map_s
>  	 * skip over possible up to 2 operands to get to address, e.g.:
>  	 * tbnz	 w0, #26, ffff0000083cd190 <security_file_permission+0xd0>
>  	 */
> -	if (c++ != NULL) {
> +	if (c != NULL) {
> +		c++;
>  		ops->target.addr = strtoull(c, NULL, 16);
>  		if (!ops->target.addr) {
>  			c = strchr(c, ',');
>  			c = validate_comma(c, ops);
> -			if (c++ != NULL)
> +			if (c != NULL) {
> +				c++;
>  				ops->target.addr = strtoull(c, NULL, 16);
> +			}
>  		}
>  	} else {
>  		ops->target.addr = strtoull(ops->raw, NULL, 16);

It is undefined behavior, but works correctly with GCC and Clang. In
Gnulib, we allow it and suggest using -fno-sanitize=pointer-overflow
instead [1].

But I can understand that is not every projects preference. Therefore,
this change looks good to me.

Reviewed-by: Collin Funk <collin.funk1@...il.com>

Collin

[1] https://www.gnu.org/software/gnulib/manual/html_node/Unsupported-Platforms.html