linux-kernel - [PATCH v2 5/7] tools/nolibc: fix integer overflow in i{64,}toa

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Message-Id: <20250419-nolibc-ubsan-v2-5-060b8a016917@weissschuh.net>
Date: Sat, 19 Apr 2025 12:46:22 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>, "Paul E. McKenney" <paulmck@...nel.org>, 
 Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2 5/7] tools/nolibc: fix integer overflow in i{64,}toa_r()
 and

In twos complement the most negative number can not be negated.

Fixes: b1c21e7d99cd ("tools/nolibc/stdlib: add i64toa() and u64toa()")
Fixes: 66c397c4d2e1 ("tools/nolibc/stdlib: replace the ltoa() function with more efficient ones")
Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 tools/include/nolibc/stdlib.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/include/nolibc/stdlib.h b/tools/include/nolibc/stdlib.h
index 86ad378ab1ea220559d5ab1adc4bb9972977ba9e..32b3038002c16864cf66a71ae9fa3825f995b09c 100644
--- a/tools/include/nolibc/stdlib.h
+++ b/tools/include/nolibc/stdlib.h
@@ -275,7 +275,7 @@ int itoa_r(long in, char *buffer)
 	int len = 0;

 	if (in < 0) {
-		in = -in;
+		in = -(unsigned long)in;
 		*(ptr++) = '-';
 		len++;
 	}
@@ -411,7 +411,7 @@ int i64toa_r(int64_t in, char *buffer)
 	int len = 0;

 	if (in < 0) {
-		in = -in;
+		in = -(uint64_t)in;
 		*(ptr++) = '-';
 		len++;
 	}

-- 
2.49.0