From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu, 24 Apr 2025 12:41:11 +0000 (-0300)
Subject: stdio-common: Fix UB on stdio-common/vfprintf-process-arg.c
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b3a4a701dc570fa806eac0a0aec12f12ee719ab;p=thirdparty%2Fglibc.git

stdio-common: Fix UB on stdio-common/vfprintf-process-arg.c

On i686 debug/tst-sprintf-fortify-unchecked triggers:

UBSAN: Undefined behaviour in vfprintf-process-arg.c:41:57 negation of 9223372036854775808 cannot be represented in type 'long long int'
---

diff --git a/stdio-common/vfprintf-process-arg.c b/stdio-common/vfprintf-process-arg.c
index a41feb2c47..fd23213e7e 100644
--- a/stdio-common/vfprintf-process-arg.c
+++ b/stdio-common/vfprintf-process-arg.c
@@ -38,7 +38,8 @@ LABEL (form_integer):
     {
       long long int signed_number = process_arg_long_long_int ();
       is_negative = signed_number < 0;
-      number.longlong = is_negative ? (- signed_number) : signed_number;
+      number.longlong = is_negative ? (- (unsigned long long) signed_number)
+				    : signed_number;
 
       goto LABEL (longlong_number);
     }