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From:   Sohom Datta <sohomdatta1@gmail.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>
Cc:     Sohom Datta <sohomdatta1+git@gmail.com>,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] Prevent normalize() from reading into undefined memory
Date:   Sun,  4 Dec 2022 16:28:35 +0530
Message-Id: <20221204105836.1012885-1-sohomdatta1+git@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The current implementation does not account for a
trailing backslash followed by a null-byte. If a
null-byte is encountered following a backslash,
normalize() will continue reading (and potentially
writing) into garbage memory ignoring the EOS
null-byte.

Signed-off-by: Sohom Datta <sohomdatta1+git@gmail.com>
---
 tools/perf/util/expr.l | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/expr.l b/tools/perf/util/expr.l
index 0168a9637330..d47de5f270a8 100644
--- a/tools/perf/util/expr.l
+++ b/tools/perf/util/expr.l
@@ -42,8 +42,11 @@ static char *normalize(char *str, int runtime)
 	char *dst = str;
 
 	while (*str) {
-		if (*str == '\\')
+		if (*str == '\\') {
 			*dst++ = *++str;
+			if (!*str)
+				break;
+		}
 		else if (*str == '?') {
 			char *paramval;
 			int i = 0;
-- 
2.38.1