In case one of the allocations fails.
For example:
AddressSanitizer:DEADLYSIGNAL
=================================================================
==17==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000000 (pc 0x7fb352a476e5 bp 0x7ffe45154850 sp 0x7ffe45154008 T0)
==17==The signal is caused by a READ memory access.
==17==Hint: address points to the zero page.
SCARINESS: 10 (null-deref)
#0 0x7fb352a476e5 (/lib/x86_64-linux-gnu/libc.so.6+0x1886e5) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#1 0x435878 in __interceptor_strlen /src/llvm-project/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc
#2 0x4de1e4 in LLVMFuzzerTestOneInput /work/build/../../src/systemd/src/fuzz/fuzz-calendarspec.c:20:21
#3 0x4deea8 in NaloFuzzerTestOneInput (/build/fuzz-calendarspec+0x4deea8)
#4 0x4fde33 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:611:15
#5 0x4fd61a in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool, bool*) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:514:3
#6 0x4fece9 in fuzzer::Fuzzer::MutateAndTestOne() /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:757:19
#7 0x4ff9b5 in fuzzer::Fuzzer::Loop(std::__Fuzzer::vector<fuzzer::SizedFile, std::__Fuzzer::allocator<fuzzer::SizedFile> >&) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerLoop.cpp:895:5
#8 0x4eed1f in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:912:6
#9 0x4ef5e8 in LLVMFuzzerRunDriver /src/llvm-project/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:925:10
#10 0x4df105 in main (/build/fuzz-calendarspec+0x4df105)
#11 0x7fb3528e3082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082) (BuildId: 1878e6b475720c7c51969e69ab2d276fae6d1dee)
#12 0x41f80d in _start (/build/fuzz-calendarspec+0x41f80d)
Found by Nallocfuzz.
-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.
Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state
Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.
In some places, initialization is dropped if unnecessary.
The man page says nothing about "e". Glibc clearly accepts it without fuss, but
it is meaningless for a memory object (and probably doesn't work). This use is
not portable, so let's avoid it.
The compiler may decide computations like these are not doing anything
and decide to optimize them away. This would defeat the whole fuzzing
exercise. This macro will force the compiler to materialize the value
no matter what. It should be less prone to accidents compared to using
log functions, which would either slow things down or still optimize the
value away (or simply move it into the if branch the log macros create).
The benefit over assert_se would be that no requirement is made on the
value itself. If we are fine getting a string of any size (including
zero), an assert_se would either create a noisy compiler warning about
conditions that would alawys be met or yet again optimize the whole
thing away.
Without the size limits, oss-fuzz creates huge samples that time out. Usually
this is because some of our code has bad algorithmic complexity. For data like
configuration samples we don't need to care about this: non-rogue configs are
rarely more than a few items, and a bit of a slowdown with a few hundred items
is acceptable. This wouldn't be OK for processing of untrusted data though.
We need to set the limit in two ways: through .options and in the code. The
first because it nicely allows libFuzzer to avoid wasting time, and the second
because fuzzers like hongfuzz and afl don't support .options.
While at it, let's fix an off-by-one (65535 is the largest offset for a
power-of-two size, but we're checking the size here).
Co-authored-by: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Coverage data shows that we didn't test calendar_spec_next_usec() and
associated functions at all.
The input samples so far were only used until the first NUL. We take advantage
of that by using the part until the second NUL as the starting timestamp,
retaining backwards compatibility for how the first part is used.
calendar_spec_from_string() already calls calendar_spec_normalize(), so
there is no point in calling it from the fuzzer. Once that's removed, there's
just one internal caller and it can be made static.
Given we have two different types for the journal object flags and the
Compression enum, let's make the latter a regular non-sparse enum, and
thus remove some surprises. We have to convert anyway between the two,
and already do via COMPRESSION_FROM_OBJECT().
The compression helpers are used both in journal code and in coredump
code, and there's a good chance we'll use them later for other stuff.
Let's hence move them into src/basic/, to make them a proper internal
API we can use from everywhere where that's desirable. (pstore might be
a candidate, for example)
No real code changes, just some moving around, build system
rearrangements, and stripping of journal-def.h inclusion.
It wasn't picked up automatically because it's not in
test/fuzz/fuzz-fido-id-desc/. But looking at the contents, it doesn't seem to
be in the expected input format either.
We recently started making more use of malloc_usable_size() and rely on
it (see the string_erase() story). Given that we don't really support
sytems where malloc_usable_size() cannot be trusted beyond statistics
anyway, let's go fully in and rework GREEDY_REALLOC() on top of it:
instead of passing around and maintaining the currenly allocated size
everywhere, let's just derive it automatically from
malloc_usable_size().
I am mostly after this for the simplicity this brings. It also brings
minor efficiency improvements I guess, but things become so much nicer
to look at if we can avoid these allocation size variables everywhere.
Note that the malloc_usable_size() man page says relying on it wasn't
"good programming practice", but I think it does this for reasons that
don't apply here: the greedy realloc logic specifically doesn't rely on
the returned extra size, beyond the fact that it is equal or larger than
what was requested.
(This commit was supposed to be a quick patch btw, but apparently we use
the greedy realloc stuff quite a bit across the codebase, so this ends
up touching *a*lot* of code.)
No functional change, just moving a bunch of things around. Before
we needed a rather complicated setup to test hostname_setup(), because
the code was in src/core/. When things are moved to src/shared/
we can just test it as any function.
The test is still "unsafe" because hostname_setup() may modify the
hostname.
Frantisek Sumsal
Yu Watanabe
Jan Janssen
Zbigniew Jędrzejewski-Szmek
Li kunyu
David Tardon
Luca Boccassi
Lennart Poettering
Evgeny Vereshchagin
Susant Sahani
Yu, Li-Yu