basic/ellipsize: do not assume the string is NUL-terminated when length is given

oss-fuzz flags this as:

==1==WARNING: MemorySanitizer: use-of-uninitialized-value

0. 0x7fce77519ca5 in ascii_is_valid systemd/src/basic/utf8.c:252:9
1. 0x7fce774d203c in ellipsize_mem systemd/src/basic/string-util.c:544:13
2. 0x7fce7730a299 in print_multiline systemd/src/shared/logs-show.c:244:37
3. 0x7fce772ffdf3 in output_short systemd/src/shared/logs-show.c:495:25
4. 0x7fce772f5a27 in show_journal_entry systemd/src/shared/logs-show.c:1077:15
5. 0x7fce772f66ad in show_journal systemd/src/shared/logs-show.c:1164:29
6. 0x4a2fa0 in LLVMFuzzerTestOneInput systemd/src/fuzz/fuzz-journal-remote.c:64:21
...

I didn't reproduce the issue, but this looks like an obvious error: the length
is specified, so we shouldn't use the string with any functions for normal
C-strings.

diff --git a/src/basic/format-table.c b/src/basic/format-table.c
index 774f1f17d2e1677c72beec252f2b18c2c2b1e4d5..fe7c351939e0018e74014d5f1b9c0094b40eecd2 100644 (file)
--- a/src/basic/format-table.c
+++ b/src/basic/format-table.c
@@ -1174,7 +1174,7 @@ int table_print(Table *t, FILE *f) {
                         if (l > width[j]) {
                                 /* Field is wider than allocated space. Let's ellipsize */
 
-                                buffer = ellipsize_mem(field, (size_t) -1, width[j], d->ellipsize_percent);
+                                buffer = ellipsize(field, width[j], d->ellipsize_percent);
                                 if (!buffer)
                                         return -ENOMEM;
 

diff --git a/src/basic/string-util.c b/src/basic/string-util.c
index 13456f101454846a8e021fe37099df79371740a7..1f8bf3d4de5cf46a72fc24c33efc7a54cb4128da 100644 (file)
--- a/src/basic/string-util.c
+++ b/src/basic/string-util.c
@@ -545,7 +545,7 @@ char *ellipsize_mem(const char *s, size_t old_length, size_t new_length, unsigne
                 return strdup("");
 
         /* If no multibyte characters use ascii_ellipsize_mem for speed */
-        if (ascii_is_valid(s))
+        if (ascii_is_valid_n(s, old_length))
                 return ascii_ellipsize_mem(s, old_length, new_length, percent);
 
         x = ((new_length - 1) * percent) / 100;