1 // Copyright © 2025 Microsoft 2 // 3 // SPDX-License-Identifier: Apache-2.0 4 5 #![no_main] 6 7 use std::os::unix::io::{AsRawFd, FromRawFd}; 8 use std::sync::Arc; 9 10 use libfuzzer_sys::{fuzz_target, Corpus}; 11 use seccompiler::SeccompAction; 12 use virtio_devices::vsock::tests::TestBackend; 13 use virtio_devices::{VirtioDevice, VirtioInterrupt, VirtioInterruptType}; 14 use virtio_queue::{Queue, QueueT}; 15 use vm_memory::bitmap::AtomicBitmap; 16 use vm_memory::{Bytes, GuestAddress, GuestMemoryAtomic}; 17 use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK}; 18 use vmm_sys_util::tempdir::TempDir; 19 20 type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>; 21 22 macro_rules! align { 23 ($n:expr, $align:expr) => {{ 24 $n.div_ceil($align) * $align 25 }}; 26 } 27 28 const QUEUE_DATA_SIZE: usize = 4; 29 const MEM_SIZE: usize = 1 * 1024 * 1024; 30 31 // Max entries in the queue. 32 const QUEUE_SIZE: u16 = 256; 33 // Descriptor table alignment 34 const DESC_TABLE_ALIGN_SIZE: u64 = 16; 35 // Available ring alignment 36 const AVAIL_RING_ALIGN_SIZE: u64 = 2; 37 // Used ring alignment 38 const USED_RING_ALIGN_SIZE: u64 = 4; 39 // Descriptor table size 40 const DESC_TABLE_SIZE: u64 = 16_u64 * QUEUE_SIZE as u64; 41 // Available ring size 42 const AVAIL_RING_SIZE: u64 = 6_u64 + 2 * QUEUE_SIZE as u64; 43 // Used ring size 44 const USED_RING_SIZE: u64 = 6_u64 + 8 * QUEUE_SIZE as u64; 45 46 // Guest memory gap 47 const GUEST_MEM_GAP: u64 = 1 * 1024 * 1024; 48 // Guest physical address for descriptor table. 49 const DESC_TABLE_ADDR: u64 = align!(MEM_SIZE as u64 + GUEST_MEM_GAP, DESC_TABLE_ALIGN_SIZE); 50 // Guest physical address for available ring 51 const AVAIL_RING_ADDR: u64 = align!(DESC_TABLE_ADDR + DESC_TABLE_SIZE, AVAIL_RING_ALIGN_SIZE); 52 // Guest physical address for used ring 53 const USED_RING_ADDR: u64 = align!(AVAIL_RING_ADDR + AVAIL_RING_SIZE, USED_RING_ALIGN_SIZE); 54 // Virtio-queue size in bytes 55 const QUEUE_BYTES_SIZE: usize = (USED_RING_ADDR + USED_RING_SIZE - DESC_TABLE_ADDR) as usize; 56 57 fuzz_target!(|bytes: &[u8]| -> Corpus { 58 if bytes.len() < (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE) 59 || bytes.len() > (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE + MEM_SIZE) 60 { 61 return Corpus::Reject; 62 } 63 64 let queue_data = &bytes[..QUEUE_DATA_SIZE]; 65 let queue_bytes = &bytes[QUEUE_DATA_SIZE..QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE]; 66 let mem_bytes = &bytes[QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE..]; 67 68 let q = setup_virt_queue(queue_data.try_into().unwrap()); 69 70 let tmp_dir = TempDir::new_with_prefix("/tmp/fuzz_virtio_vsock").unwrap(); 71 let vsock_path = tmp_dir.as_path().join("vsock.sock"); 72 73 let backend = TestBackend::new(); 74 75 // Setup the guest memory with the input bytes 76 let mem = GuestMemoryMmap::from_ranges(&[ 77 (GuestAddress(0), MEM_SIZE), 78 (GuestAddress(DESC_TABLE_ADDR), QUEUE_BYTES_SIZE), 79 ]) 80 .unwrap(); 81 if mem 82 .write_slice(queue_bytes, GuestAddress(DESC_TABLE_ADDR)) 83 .is_err() 84 { 85 return Corpus::Reject; 86 } 87 if mem.write_slice(mem_bytes, GuestAddress(0 as u64)).is_err() { 88 return Corpus::Reject; 89 } 90 let guest_memory = GuestMemoryAtomic::new(mem); 91 92 let evt = EventFd::new(0).unwrap(); 93 let queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(evt.as_raw_fd())) }; 94 95 // Kick the 'queue' event before activate the rng device 96 queue_evt.write(1).unwrap(); 97 98 let mut vsock = virtio_devices::Vsock::new( 99 "fuzzer_vsock".to_owned(), 100 0, 101 vsock_path, 102 backend, 103 false, 104 SeccompAction::Allow, 105 EventFd::new(EFD_NONBLOCK).unwrap(), 106 None, 107 ) 108 .unwrap(); 109 110 vsock 111 .activate( 112 guest_memory, 113 Arc::new(NoopVirtioInterrupt {}), 114 vec![(0, q, evt)], 115 ) 116 .ok(); 117 118 // Wait for the events to finish and vsock device worker thread to return 119 vsock.wait_for_epoll_threads(); 120 121 Corpus::Keep 122 }); 123 124 pub struct NoopVirtioInterrupt {} 125 126 impl VirtioInterrupt for NoopVirtioInterrupt { 127 fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> { 128 Ok(()) 129 } 130 } 131 132 fn setup_virt_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue { 133 let mut q = Queue::new(QUEUE_SIZE).unwrap(); 134 q.set_next_avail(bytes[0] as u16); // 'u8' is enough given the 'QUEUE_SIZE' is small 135 q.set_next_used(bytes[1] as u16); 136 q.set_event_idx(bytes[2] % 2 != 0); 137 q.set_size(bytes[3] as u16 % QUEUE_SIZE); 138 139 q.try_set_desc_table_address(GuestAddress(DESC_TABLE_ADDR)) 140 .unwrap(); 141 q.try_set_avail_ring_address(GuestAddress(AVAIL_RING_ADDR)) 142 .unwrap(); 143 q.try_set_used_ring_address(GuestAddress(USED_RING_ADDR)) 144 .unwrap(); 145 q.set_ready(true); 146 147 q 148 } 149