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fuzz: block: Setup the virt queue based on the fuzzed input bytes

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Instead of always fuzzing virt-queues with default values (mostly 0s),
the fuzzer now initializes the virt-queue based on the fuzzed input
bytes, such as the tail position of the available ring, queue size
selected by driver, descriptor table address, available ring address,
used ring address, etc. In this way, the fuzzer can explore the
virtio-block code path with various virt-queue setup.

Signed-off-by: Bo Chen <chen.bo@intel.com>
This commit is contained in:
Bo Chen 2022-08-30 17:41:19 -07:00 committed by Sebastien Boeuf
parent dc2365bfd0
commit 742d6858f7
1 changed files with 42 additions and 16 deletions
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58
fuzz/fuzz_targets/block.rs
View File

@ -24,32 +24,22 @@ use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};
type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;
const MEM_SIZE: u64 = 256 * 1024 * 1024;
const QUEUE_DATA_SIZE: usize = 28;
const MEM_SIZE: usize = 256 * 1024 * 1024;
const QUEUE_SIZE: u16 = 16; // Max entries in the queue.
fuzz_target!(|bytes| {
if bytes.len() as u64 > MEM_SIZE {
if bytes.len() < QUEUE_DATA_SIZE || bytes.len() > (QUEUE_DATA_SIZE + MEM_SIZE) {
return;
}
let mem = GuestMemoryMmap::from_ranges(&[(GuestAddress(0), MEM_SIZE as usize)]).unwrap();
if mem.write_slice(bytes, GuestAddress(0 as u64)).is_err() {
return;
}
let guest_memory = GuestMemoryAtomic::new(mem);
let mut q = Queue::new(QUEUE_SIZE).unwrap();
q.set_ready(true);
q.set_size(QUEUE_SIZE / 2);
let evt = EventFd::new(0).unwrap();
let queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(evt.as_raw_fd())) };
let queue_data = &bytes[..QUEUE_DATA_SIZE];
let mem_bytes = &bytes[QUEUE_DATA_SIZE..];
// Create a virtio-block device backed by a synchronous raw file
let shm = memfd_create(&ffi::CString::new("fuzz").unwrap(), 0).unwrap();
let disk_file: File = unsafe { File::from_raw_fd(shm) };
let qcow_disk = Box::new(RawFileDiskSync::new(disk_file)) as Box<dyn DiskFile>;
let mut block = Block::new(
"tmp".to_owned(),
qcow_disk,
@ -64,6 +54,19 @@ fuzz_target!(|bytes| {
)
.unwrap();
// Setup the virt queue with the input bytes
let q = setup_virt_queue(queue_data.try_into().unwrap());
// Setup the guest memory with the input bytes
let mem = GuestMemoryMmap::from_ranges(&[(GuestAddress(0), MEM_SIZE)]).unwrap();
if mem.write_slice(mem_bytes, GuestAddress(0 as u64)).is_err() {
return;
}
let guest_memory = GuestMemoryAtomic::new(mem);
let evt = EventFd::new(0).unwrap();
let queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(evt.as_raw_fd())) };
// Kick the 'queue' event before activate the block device
queue_evt.write(1).unwrap();
@ -96,3 +99,26 @@ impl VirtioInterrupt for NoopVirtioInterrupt {
Ok(())
}
}
fn setup_virt_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue {
let mut q = Queue::new(QUEUE_SIZE).unwrap();
q.set_next_avail(bytes[0] as u16); // 'u8' is enough given the 'QUEUE_SIZE' is small
q.set_next_used(bytes[1] as u16);
q.set_event_idx(bytes[2] % 2 != 0);
q.set_size(bytes[3] as u16 % QUEUE_SIZE);
q.set_desc_table_address(
Some(u32::from_le_bytes(bytes[4..8].try_into().unwrap())),
Some(u32::from_le_bytes(bytes[8..12].try_into().unwrap())),
);
q.set_avail_ring_address(
Some(u32::from_le_bytes(bytes[12..16].try_into().unwrap())),
Some(u32::from_le_bytes(bytes[16..20].try_into().unwrap())),
);
q.set_used_ring_address(
Some(u32::from_le_bytes(bytes[20..24].try_into().unwrap())),
Some(u32::from_le_bytes(bytes[24..28].try_into().unwrap())),
);
q.set_ready(true);
q
}