Hi Alex, Thanks for the nice general fuzzer implementation, looks pretty exciting. Are there any future plans discussion which i can read or maybe join? I have some ideas about it so it could be great to syncronize.
Regards, Dima. On Wed, Jul 22, 2020 at 11:39:21PM -0400, Alexander Bulekov wrote: > This is a general virtual-device fuzzer, designed to fuzz devices over Port > IO, > MMIO, and DMA. > To get started with this: > 1. Build the fuzzers (see docs/devel/fuzzing.txt) > Note: Build with --enable-sanitizers, or create a "dictionary file": > echo kw1=\"\x84\x05\x5C\x5E\" > dict > and pass it as an argument to libFuzzer with -dict=./dict > This magic value is a command separator that lets the fuzzer perform > multiple IO actions with a single input. > > 2. Pick the qemu arguments you wish to fuzz: > export QEMU_FUZZ_ARGS="-M q35 -device virtio-balloon" > > 3. Tell the fuzzer which QOM objects or MemoryRegion names to fuzz. I find > the > "info qom-tree", "info qtree" and "info mtree" commands useful for > identifying > these. Supports globbing. Here I will try to simultaneously fuzz(for no good > reason) virtio-balloon and e1000e, which is included by default in the q35: > export QEMU_FUZZ_OBJECTS='virtio* e1000*' > You can also try to fuzz the whole machine: > export QEMU_FUZZ_OBJECTS='*' > > 4. Run the fuzzer for 0 inputs. The fuzzer should output a list of > MemoryRegions/PCI Devices it will try to fuzz. Confirm that these match your > expectations. > ./i386-softmmu/qemu-fuzz-i386 --fuzz-target=general-fuzz -runs=0 > > 5. Run the fuzzer: > ./i386-softmmu/qemu-fuzz-i386 --fuzz-target=general-fuzz > > > Basically, at the core, this fuzzer is an interpreter that splits the input > into a series of commands, such as mmio_write, pio_write, etc. We structure > these commands to hit only MemoryRegions that are associated with the devices > specified in QEMU_FUZZ_OBJECTS. Additionally, these patches add "hooks" to > functions that are typically used by virtual-devices to read from RAM (DMA). > These hooks attempt to populate these DMA regions with fuzzed data, just in > time. > > Patch 1 changes the way we tell QTest to log to stderr (becomes important when > building reproducers with this fuzzer) > > Patches 2-6 add the fuzzer and the necessary DMA callbacks > > Patches 7-10 are my (very rough) attempt at integrating this into OSS-Fuzz > > Patches 11-12 contain the "reordering" and minimization scripts used to > produce a QTest reproducer for a crash. > > Additional notes: > * With the latest changes, the > fuzzer is quite effective at only targeting the device we care about, > so it will probably be beneficial to allow reboot() as an option for > resetting state, rather than fork(), for devices where that works well. > > * We have only scratched the surface for device "backends". I.e. I am using > fake null-co:// drives for block devices and SLiRP for network devices (see > scripts/oss-fuzz/general_fuzzer_configs.yml). Using more complex backends > will > likely break due to forking/threading/statefulness related reasons and will > require more work. > > * Because I still can't figure out how to make QOS do what I want, this > only maps PCI BARs on i386. For other targets, the fuzzer can still > try to do it on its own :). Only did a very simple test on ppc and arm > > * This is failing on GitLab due to a leak: > https://gitlab.com/a1xndr/qemu/-/jobs/652179729 > I am not sure how to work around it yet, since I don't think we can > free what the trace says we should free (argv from wordexp that we pass > to qemu_main). > > > Some of the issues I have found or reproduced with this fuzzer: > https://bugs.launchpad.net/bugs/1525123 > https://bugs.launchpad.net/bugs/1681439 > https://bugs.launchpad.net/bugs/1777315 > https://bugs.launchpad.net/bugs/1878034 > https://bugs.launchpad.net/bugs/1878043 > https://bugs.launchpad.net/bugs/1878054 > https://bugs.launchpad.net/bugs/1878057 > https://bugs.launchpad.net/bugs/1878067 > https://bugs.launchpad.net/bugs/1878134 > https://bugs.launchpad.net/bugs/1878136 > https://bugs.launchpad.net/bugs/1878253 > https://bugs.launchpad.net/bugs/1878255 > https://bugs.launchpad.net/bugs/1878259 > https://bugs.launchpad.net/bugs/1878263 > https://bugs.launchpad.net/bugs/1878323 > https://bugs.launchpad.net/bugs/1878641 > https://bugs.launchpad.net/bugs/1878642 > https://bugs.launchpad.net/bugs/1878645 > https://bugs.launchpad.net/bugs/1878651 > https://bugs.launchpad.net/bugs/1879223 > https://bugs.launchpad.net/bugs/1879227 > https://bugs.launchpad.net/bugs/1879531 > https://bugs.launchpad.net/bugs/1880355 > https://bugs.launchpad.net/bugs/1880539 > https://bugs.launchpad.net/bugs/1884693 > https://bugs.launchpad.net/bugs/1886362 > https://bugs.launchpad.net/bugs/1887303 > https://bugs.launchpad.net/bugs/1887309 > https://bugs.launchpad.net/bugs/697510 > > -Alex > > Alexander Bulekov (12): > fuzz: Change the way we write qtest log to stderr > fuzz: Add general virtual-device fuzzer > fuzz: Add PCI features to the general fuzzer > fuzz: Add DMA support to the generic-fuzzer > fuzz: Declare DMA Read callback function > fuzz: Add fuzzer callbacks to DMA-read functions > scripts/oss-fuzz: Add wrapper program for generic fuzzer > scripts/oss-fuzz: Add general-fuzzer build script > scripts/oss-fuzz: Add general-fuzzer configs for oss-fuzz > scripts/oss-fuzz: build the general-fuzzer configs > scripts/oss-fuzz: Add script to reorder a general-fuzzer trace > scripts/oss-fuzz: Add crash trace minimization script > > exec.c | 2 + > include/exec/memory.h | 16 + > include/exec/memory_ldst_cached.inc.h | 3 + > memory_ldst.inc.c | 4 + > scripts/oss-fuzz/build.sh | 8 +- > scripts/oss-fuzz/build_general_fuzzers.py | 62 ++ > scripts/oss-fuzz/general_fuzzer_configs.yml | 103 +++ > scripts/oss-fuzz/minimize_qtest_trace.py | 117 +++ > .../oss-fuzz/reorder_fuzzer_qtest_trace.py | 94 +++ > scripts/oss-fuzz/target.c | 40 + > softmmu/memory.c | 14 + > tests/qtest/fuzz/Makefile.include | 1 + > tests/qtest/fuzz/fuzz.c | 5 +- > tests/qtest/fuzz/general_fuzz.c | 758 ++++++++++++++++++ > 14 files changed, 1223 insertions(+), 4 deletions(-) > create mode 100755 scripts/oss-fuzz/build_general_fuzzers.py > create mode 100644 scripts/oss-fuzz/general_fuzzer_configs.yml > create mode 100755 scripts/oss-fuzz/minimize_qtest_trace.py > create mode 100755 scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py > create mode 100644 scripts/oss-fuzz/target.c > create mode 100644 tests/qtest/fuzz/general_fuzz.c > > -- > 2.27.0 >
