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.
First, ellipsize() and ellipsize_mem() should not read past the input
buffer. Those functions take an explicit length for the input data, so they
should not assume that the buffer is terminated by a nul.
Second, ellipsization was off in various cases where wide on multi-byte
characters were used.
We had some basic test for ellipsize(), but apparently it wasn't enough to
catch more serious cases.
Should fix https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=8686.
journalctl -o short would display those entries, but journalctl -o short-full
would refuse. If the entry is bad, just fall back to the receive-side realtime
timestamp like we would if it was completely missing.
We'd look for a '=' separator using memchr, i.e. ignoring any nul bytes in the
string, but then do a strndup, which would terminate on any nul byte, and then
again do a memcmp, which would access memory past the chunk allocated by strndup.
Of course, we probably shouldn't allow keys with nul bytes in them. But we
currently do, so there might be journal files like that out there. So let's fix
the journal-reading code first.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
ubsan times out because we do too many allocations:
$ valgrind build/fuzz-unit-file test/fuzz-regressions/fuzz-unit-file/oss-fuzz-6977-full
...
test/fuzz-regressions/fuzz-unit-file/oss-fuzz-6977-full... ok
==1757==
==1757== HEAP SUMMARY:
==1757== in use at exit: 0 bytes in 0 blocks
==1757== total heap usage: 199,997 allocs, 199,997 frees, 90,045,318,585 bytes allocated
...
==3256== total heap usage: 100,120 allocs, 100,120 frees, 13,097,140 bytes allocated
https://oss-fuzz.com/v2/issue/4651449704251392/6977 should now be really fixed.
e3c3d6761b was the first attempt, but even with this change, e3c3d6761b
still makes sense.
No need to go through the specifier_printf() if the path is already too long in
the unexpanded form (since specifiers increase the length of the string in all
practical cases).
In the oss-fuzz test case, valgrind reports:
total heap usage: 179,044 allocs, 179,044 frees, 72,687,755,703 bytes allocated
and the original config file is ~500kb. This isn't really a security issue,
since the config file has to be trusted any way, but just a matter of
preventing accidental resource exhaustion.
https://oss-fuzz.com/v2/issue/4651449704251392/6977
While at it, fix order of arguments in the neighbouring log_syntax() call.
The orignal reproducer from oss-fuzz depends on the hostname (via %H and %c).
The hostname needs a dash for msan to report this, so a simpler case from
@evverx with the dash hardcoded is also added.
The issue is a false positive from msan, which does not instruct stpncpy
(https://github.com/google/sanitizers/issues/926). Let's add a work-around
until this is fixed.
We have only three bits of space, i.e. 8 possible classes. Immediately reject
anything outside of that range. Add the fuzzer test case and an additional
unit test.
oss-fuzz #6908.
We probably should allow very deep calls of our recursive functions. Let's add
a limit to avoid resource exhaustion. 240 is 10 per hour (if somebody is using
this for time based triggers...), so it should be more than enough for most use
cases, and is conveniently below the 250 stack limit in msan.
oss-fuzz #6917.
gmtime_r() will return NULL in that case, and we would crash.
I committed the reproducer case in fuzz-regressions/, even though we don't have
ubsan hooked up yet. Let's add it anyway in case it is useful in the future. We
actually crash anyway when compiled with asserts, so this can be easily
reproduced without ubsan.
oss-fuzz #6886.
This seems to be a false positive in msan:
https://github.com/google/sanitizers/issues/767.
I don't see anything wrong with the code either, and valgrind does not see the
issue. Anyway, let's add the test case.
We don't have msan hooked up yet, but hopefully we'll in the future.
oss-fuzz #6884.
We currently have just one sanitizer for tests, asan, but we may add more in
the future. So let's keep the loop over the sanitizers in meson.build, but
just enable all regression cases under all sanitizers. If it fails under one
of them, it might fail under a different one.
In subsequent commits I'll add test cases which might not fail under asan,
but it's good to commit them for future use.
The test names are made more verbose:
256/257 fuzz-dns-packet:oss-fuzz-5465:address OK 0.04 s
257/257 fuzz-dns-packet:issue-7888:address OK 0.03 s
This is a bit painful because a separate build of systemd is necessary. The
tests are guarded by tests!=false and slow-tests==true. Running them is not
slow, but compilation certainly is. If this proves unwieldy, we can add a
separate option controlling those builds later.
The build for each sanitizer has its own directory, and we build all fuzzer
tests there, and then pull them out one-by-one by linking into the target
position as necessary. It would be nicer to just build the desired fuzzer, but
we need to build the whole nested build as one unit.
[I also tried making systemd and nested meson subproject. This would work
nicely, but meson does not allow that because the nested target names are the
same as the outer project names. If that is ever fixed, that would be the way
to go.]
v2:
- make sure things still work if memory sanitizer is not available
v3:
- switch to syntax which works with meson 0.42.1 found in Ubuntu
Zbigniew Jędrzejewski-Szmek