1 // Copyright © 2022 Intel Corporation
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::{VirtioDevice, VirtioInterrupt, VirtioInterruptType};
13 use virtio_queue::{Queue, QueueT};
14 use vm_memory::bitmap::AtomicBitmap;
15 use vm_memory::{Bytes, GuestAddress, GuestMemoryAtomic};
16 use vmm_sys_util::eventfd::{EventFd, EFD_NONBLOCK};
17
18 type GuestMemoryMmap = vm_memory::GuestMemoryMmap<AtomicBitmap>;
19
20 macro_rules! align {
21 ($n:expr, $align:expr) => {{
22 $n.div_ceil($align) * $align
23 }};
24 }
25
26 const QUEUE_DATA_SIZE: usize = 4;
27 const MEM_SIZE: usize = 1 * 1024 * 1024;
28
29 // Max entries in the queue.
30 const QUEUE_SIZE: u16 = 256;
31 // Descriptor table alignment
32 const DESC_TABLE_ALIGN_SIZE: u64 = 16;
33 // Available ring alignment
34 const AVAIL_RING_ALIGN_SIZE: u64 = 2;
35 // Used ring alignment
36 const USED_RING_ALIGN_SIZE: u64 = 4;
37 // Descriptor table size
38 const DESC_TABLE_SIZE: u64 = 16_u64 * QUEUE_SIZE as u64;
39 // Available ring size
40 const AVAIL_RING_SIZE: u64 = 6_u64 + 2 * QUEUE_SIZE as u64;
41 // Used ring size
42 const USED_RING_SIZE: u64 = 6_u64 + 8 * QUEUE_SIZE as u64;
43
44 // Guest memory gap
45 const GUEST_MEM_GAP: u64 = 1 * 1024 * 1024;
46 // Guest physical address for descriptor table.
47 const DESC_TABLE_ADDR: u64 = align!(MEM_SIZE as u64 + GUEST_MEM_GAP, DESC_TABLE_ALIGN_SIZE);
48 // Guest physical address for available ring
49 const AVAIL_RING_ADDR: u64 = align!(DESC_TABLE_ADDR + DESC_TABLE_SIZE, AVAIL_RING_ALIGN_SIZE);
50 // Guest physical address for used ring
51 const USED_RING_ADDR: u64 = align!(AVAIL_RING_ADDR + AVAIL_RING_SIZE, USED_RING_ALIGN_SIZE);
52 // Virtio-queue size in bytes
53 const QUEUE_BYTES_SIZE: usize = (USED_RING_ADDR + USED_RING_SIZE - DESC_TABLE_ADDR) as usize;
54
55 fuzz_target!(|bytes: &[u8]| -> Corpus {
56 if bytes.len() < (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE)
57 || bytes.len() > (QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE + MEM_SIZE)
58 {
59 return Corpus::Reject;
60 }
61
62 let mut rng = virtio_devices::Rng::new(
63 "fuzzer_rng".to_owned(),
64 "/dev/urandom",
65 false,
66 SeccompAction::Allow,
67 EventFd::new(EFD_NONBLOCK).unwrap(),
68 None,
69 )
70 .unwrap();
71
72 let queue_data = &bytes[..QUEUE_DATA_SIZE];
73 let queue_bytes = &bytes[QUEUE_DATA_SIZE..QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE];
74 let mem_bytes = &bytes[QUEUE_DATA_SIZE + QUEUE_BYTES_SIZE..];
75
76 // Setup the virt queue with the input bytes
77 let q = setup_virt_queue(queue_data.try_into().unwrap());
78
79 // Setup the guest memory with the input bytes
80 let mem = GuestMemoryMmap::from_ranges(&[
81 (GuestAddress(0), MEM_SIZE),
82 (GuestAddress(DESC_TABLE_ADDR), QUEUE_BYTES_SIZE),
83 ])
84 .unwrap();
85 if mem
86 .write_slice(queue_bytes, GuestAddress(DESC_TABLE_ADDR))
87 .is_err()
88 {
89 return Corpus::Reject;
90 }
91 if mem.write_slice(mem_bytes, GuestAddress(0 as u64)).is_err() {
92 return Corpus::Reject;
93 }
94 let guest_memory = GuestMemoryAtomic::new(mem);
95
96 let evt = EventFd::new(0).unwrap();
97 let queue_evt = unsafe { EventFd::from_raw_fd(libc::dup(evt.as_raw_fd())) };
98
99 // Kick the 'queue' event before activate the rng device
100 queue_evt.write(1).unwrap();
101
102 rng.activate(
103 guest_memory,
104 Arc::new(NoopVirtioInterrupt {}),
105 vec![(0, q, evt)],
106 )
107 .ok();
108
109 // Wait for the events to finish and rng device worker thread to return
110 rng.wait_for_epoll_threads();
111
112 Corpus::Keep
113 });
114
115 pub struct NoopVirtioInterrupt {}
116
117 impl VirtioInterrupt for NoopVirtioInterrupt {
trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error>118 fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> {
119 Ok(())
120 }
121 }
122
setup_virt_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue123 fn setup_virt_queue(bytes: &[u8; QUEUE_DATA_SIZE]) -> Queue {
124 let mut q = Queue::new(QUEUE_SIZE).unwrap();
125 q.set_next_avail(bytes[0] as u16); // 'u8' is enough given the 'QUEUE_SIZE' is small
126 q.set_next_used(bytes[1] as u16);
127 q.set_event_idx(bytes[2] % 2 != 0);
128 q.set_size(bytes[3] as u16 % QUEUE_SIZE);
129
130 q.try_set_desc_table_address(GuestAddress(DESC_TABLE_ADDR))
131 .unwrap();
132 q.try_set_avail_ring_address(GuestAddress(AVAIL_RING_ADDR))
133 .unwrap();
134 q.try_set_used_ring_address(GuestAddress(USED_RING_ADDR))
135 .unwrap();
136 q.set_ready(true);
137
138 q
139 }
140