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 {
trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error>127 fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> {
128 Ok(())
129 }
130 }
131
setup_virt_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue132 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