linux-kernel - [PATCH v1] perf string: Avoid undefined NULL+1

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Message-Id: <20241120065224.286813-1-irogers@google.com>
Date: Tue, 19 Nov 2024 22:52:24 -0800
From: Ian Rogers <irogers@...gle.com>
To: 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>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, 
	"Masami Hiramatsu (Google)" <mhiramat@...nel.org>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: [PATCH v1] perf string: Avoid undefined NULL+1

While the value NULL+1 is never used it triggers a ubsan
warning. Restructure and comment the loop to avoid this.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/string.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
index 308fc7ec88cc..c0e927bbadf6 100644
--- a/tools/perf/util/string.c
+++ b/tools/perf/util/string.c
@@ -254,11 +254,20 @@ char *strpbrk_esc(char *str, const char *stopset)
 
 	do {
 		ptr = strpbrk(str, stopset);
-		if (ptr == str ||
-		    (ptr == str + 1 && *(ptr - 1) != '\\'))
+		if (!ptr) {
+			/* stopset not in str. */
 			break;
+		}
+		if (ptr == str) {
+			/* stopset character is first in str. */
+			break;
+		}
+		if (ptr == str + 1 && str[0] != '\\') {
+			/* stopset chacter is second and wasn't preceded by a '\'. */
+			break;
+		}
 		str = ptr + 1;
-	} while (ptr && *(ptr - 1) == '\\' && *(ptr - 2) != '\\');
+	} while (ptr[-1] == '\\' && ptr[-2] != '\\');
 
 	return ptr;
 }
-- 
2.47.0.371.ga323438b13-goog