From: Frantisek Sumsal <frantisek@sumsal.cz>
Date: Sun, 13 Mar 2022 13:45:03 +0000 (+0100)
Subject: macro: account for negative values in DECIMAL_STR_WIDTH()
X-Git-Tag: v251-rc1~157^2~2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e3dd9ea8ea4510221f73071ad30ee657ca77565d;p=thirdparty%2Fsystemd.git

macro: account for negative values in DECIMAL_STR_WIDTH()

With negative numbers we wouldn't account for the minus sign, thus
returning a string with one character too short, triggering buffer
overflows in certain situations.
---

diff --git a/src/basic/macro.h b/src/basic/macro.h
index aa04039e804..9e62f9c71c8 100644
--- a/src/basic/macro.h
+++ b/src/basic/macro.h
@@ -319,13 +319,13 @@ static inline int __coverity_check_and_return__(int condition) {
              sizeof(type) <= 4 ? 10U :                                  \
              sizeof(type) <= 8 ? 20U : sizeof(int[-2*(sizeof(type) > 8)])))
 
-#define DECIMAL_STR_WIDTH(x)                            \
-        ({                                              \
-                typeof(x) _x_ = (x);                    \
-                size_t ans = 1;                         \
-                while ((_x_ /= 10) != 0)                \
-                        ans++;                          \
-                ans;                                    \
+#define DECIMAL_STR_WIDTH(x)                                      \
+        ({                                                        \
+                typeof(x) _x_ = (x);                              \
+                size_t ans = IS_SIGNED_INTEGER_TYPE(_x_) ? 2 : 1; \
+                while ((_x_ /= 10) != 0)                          \
+                        ans++;                                    \
+                ans;                                              \
         })
 
 #define SWAP_TWO(x, y) do {                        \