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

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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.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2018-06-09 13:41:44 +02:00
parent 4215ed6dbd
commit 21e4e3e06f
4 changed files with 11 additions and 2 deletions
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2
src/basic/string-util.c
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@@ -541,7 +541,7 @@ 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;