From 6fb0569065b56019850a25c2b235d7119bdb0ae6 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Fri, 12 Jul 2019 16:17:51 +0200
Subject: [PATCH] util-lib: [static] array argument sizes are apparently not OK
 for NULL parameters
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Let's drop the 'static' logic when a parameter can be NULL.

I think asan/ubsan are right here, judging by the C99 spec language:

"A declaration of a parameter as ‘‘array of type’’ shall be adjusted to
‘‘qualified pointer to type’’, where the type qualifiers (if any) are
those specified within the [ and ] of the array type derivation. If the
keyword static also appears within the [ and ] of the array type
derivation, then for each call to the function, the value of the
corresponding actual argument shall provide access to the first element
of an array with at least as many elements as specified by the size
expression."

If we specify NULL, then we certainly don't pvode access to any valid
array.

Fixes: #13039
---
 src/basic/string-util.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 7c487fb9a34..9586b3940eb 100644
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -725,10 +725,17 @@ char *strreplace(const char *text, const char *old_string, const char *new_strin
         return ret;
 }
 
-static void advance_offsets(ssize_t diff, size_t offsets[static 2], size_t shift[static 2], size_t size) {
+static void advance_offsets(
+                ssize_t diff,
+                size_t offsets[2], /* note: we can't use [static 2] here, since this may be NULL */
+                size_t shift[static 2],
+                size_t size) {
+
         if (!offsets)
                 return;
 
+        assert(shift);
+
         if ((size_t) diff < offsets[0])
                 shift[0] += size;
         if ((size_t) diff < offsets[1])
@@ -844,8 +851,7 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz, size_t highlight[2]) {
 
         fclose(f);
 
-        free(*ibuf);
-        *ibuf = obuf;
+        free_and_replace(*ibuf, obuf);
 
         if (_isz)
                 *_isz = osz;
@@ -855,7 +861,7 @@ char *strip_tab_ansi(char **ibuf, size_t *_isz, size_t highlight[2]) {
                 highlight[1] += shift[1];
         }
 
-        return obuf;
+        return *ibuf;
 }
 
 char *strextend_with_separator(char **x, const char *separator, ...) {