fuzz: add virtio-net fuzz target

The virtio-net fuzz target feeds inputs to all three virtio-net
virtqueues, and uses forking to avoid leaking state between fuzz runs.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Message-id: 20200220041118.23264-21-alxndr@bu.edu
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/qtest/fuzz/Makefile.include

@@ -8,6 +8,7 @@ fuzz-obj-y += tests/qtest/fuzz/qos_fuzz.o
 
 # Targets
 fuzz-obj-y += tests/qtest/fuzz/i440fx_fuzz.o
+fuzz-obj-y += tests/qtest/fuzz/virtio_net_fuzz.o
 
 FUZZ_CFLAGS += -I$(SRC_PATH)/tests -I$(SRC_PATH)/tests/qtest
 

tests/qtest/fuzz/virtio_net_fuzz.c

@@ -0,0 +1,198 @@
+/*
+ * virtio-net Fuzzing Target
+ *
+ * Copyright Red Hat Inc., 2019
+ *
+ * Authors:
+ *  Alexander Bulekov   <alxndr@bu.edu>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "standard-headers/linux/virtio_config.h"
+#include "tests/qtest/libqtest.h"
+#include "tests/qtest/libqos/virtio-net.h"
+#include "fuzz.h"
+#include "fork_fuzz.h"
+#include "qos_fuzz.h"
+
+
+#define QVIRTIO_NET_TIMEOUT_US (30 * 1000 * 1000)
+#define QVIRTIO_RX_VQ 0
+#define QVIRTIO_TX_VQ 1
+#define QVIRTIO_CTRL_VQ 2
+
+static int sockfds[2];
+static bool sockfds_initialized;
+
+static void virtio_net_fuzz_multi(QTestState *s,
+        const unsigned char *Data, size_t Size, bool check_used)
+{
+    typedef struct vq_action {
+        uint8_t queue;
+        uint8_t length;
+        uint8_t write;
+        uint8_t next;
+        uint8_t rx;
+    } vq_action;
+
+    uint32_t free_head = 0;
+
+    QGuestAllocator *t_alloc = fuzz_qos_alloc;
+
+    QVirtioNet *net_if = fuzz_qos_obj;
+    QVirtioDevice *dev = net_if->vdev;
+    QVirtQueue *q;
+    vq_action vqa;
+    while (Size >= sizeof(vqa)) {
+        memcpy(&vqa, Data, sizeof(vqa));
+        Data += sizeof(vqa);
+        Size -= sizeof(vqa);
+
+        q = net_if->queues[vqa.queue % 3];
+
+        vqa.length = vqa.length >= Size ? Size :  vqa.length;
+
+        /*
+         * Only attempt to write incoming packets, when using the socket
+         * backend. Otherwise, always place the input on a virtqueue.
+         */
+        if (vqa.rx && sockfds_initialized) {
+            write(sockfds[0], Data, vqa.length);
+        } else {
+            vqa.rx = 0;
+            uint64_t req_addr = guest_alloc(t_alloc, vqa.length);
+            /*
+             * If checking used ring, ensure that the fuzzer doesn't trigger
+             * trivial asserion failure on zero-zied buffer
+             */
+            qtest_memwrite(s, req_addr, Data, vqa.length);
+
+
+            free_head = qvirtqueue_add(s, q, req_addr, vqa.length,
+                    vqa.write, vqa.next);
+            qvirtqueue_add(s, q, req_addr, vqa.length, vqa.write , vqa.next);
+            qvirtqueue_kick(s, dev, q, free_head);
+        }
+
+        /* Run the main loop */
+        qtest_clock_step(s, 100);
+        flush_events(s);
+
+        /* Wait on used descriptors */
+        if (check_used && !vqa.rx) {
+            gint64 start_time = g_get_monotonic_time();
+            /*
+             * normally, we could just use qvirtio_wait_used_elem, but since we
+             * must manually run the main-loop for all the bhs to run, we use
+             * this hack with flush_events(), to run the main_loop
+             */
+            while (!vqa.rx && q != net_if->queues[QVIRTIO_RX_VQ]) {
+                uint32_t got_desc_idx;
+                /* Input led to a virtio_error */
+                if (dev->bus->get_status(dev) & VIRTIO_CONFIG_S_NEEDS_RESET) {
+                    break;
+                }
+                if (dev->bus->get_queue_isr_status(dev, q) &&
+                        qvirtqueue_get_buf(s, q, &got_desc_idx, NULL)) {
+                    g_assert_cmpint(got_desc_idx, ==, free_head);
+                    break;
+                }
+                g_assert(g_get_monotonic_time() - start_time
+                        <= QVIRTIO_NET_TIMEOUT_US);
+
+                /* Run the main loop */
+                qtest_clock_step(s, 100);
+                flush_events(s);
+            }
+        }
+        Data += vqa.length;
+        Size -= vqa.length;
+    }
+}
+
+static void virtio_net_fork_fuzz(QTestState *s,
+        const unsigned char *Data, size_t Size)
+{
+    if (fork() == 0) {
+        virtio_net_fuzz_multi(s, Data, Size, false);
+        flush_events(s);
+        _Exit(0);
+    } else {
+        wait(NULL);
+    }
+}
+
+static void virtio_net_fork_fuzz_check_used(QTestState *s,
+        const unsigned char *Data, size_t Size)
+{
+    if (fork() == 0) {
+        virtio_net_fuzz_multi(s, Data, Size, true);
+        flush_events(s);
+        _Exit(0);
+    } else {
+        wait(NULL);
+    }
+}
+
+static void virtio_net_pre_fuzz(QTestState *s)
+{
+    qos_init_path(s);
+    counter_shm_init();
+}
+
+static void *virtio_net_test_setup_socket(GString *cmd_line, void *arg)
+{
+    int ret = socketpair(PF_UNIX, SOCK_STREAM, 0, sockfds);
+    g_assert_cmpint(ret, !=, -1);
+    fcntl(sockfds[0], F_SETFL, O_NONBLOCK);
+    sockfds_initialized = true;
+    g_string_append_printf(cmd_line, " -netdev socket,fd=%d,id=hs0 ",
+                           sockfds[1]);
+    return arg;
+}
+
+static void *virtio_net_test_setup_user(GString *cmd_line, void *arg)
+{
+    g_string_append_printf(cmd_line, " -netdev user,id=hs0 ");
+    return arg;
+}
+
+static void register_virtio_net_fuzz_targets(void)
+{
+    fuzz_add_qos_target(&(FuzzTarget){
+            .name = "virtio-net-socket",
+            .description = "Fuzz the virtio-net virtual queues. Fuzz incoming "
+            "traffic using the socket backend",
+            .pre_fuzz = &virtio_net_pre_fuzz,
+            .fuzz = virtio_net_fork_fuzz,},
+            "virtio-net",
+            &(QOSGraphTestOptions){.before = virtio_net_test_setup_socket}
+            );
+
+    fuzz_add_qos_target(&(FuzzTarget){
+            .name = "virtio-net-socket-check-used",
+            .description = "Fuzz the virtio-net virtual queues. Wait for the "
+            "descriptors to be used. Timeout may indicate improperly handled "
+            "input",
+            .pre_fuzz = &virtio_net_pre_fuzz,
+            .fuzz = virtio_net_fork_fuzz_check_used,},
+            "virtio-net",
+            &(QOSGraphTestOptions){.before = virtio_net_test_setup_socket}
+            );
+    fuzz_add_qos_target(&(FuzzTarget){
+            .name = "virtio-net-slirp",
+            .description = "Fuzz the virtio-net virtual queues with the slirp "
+            " backend. Warning: May result in network traffic emitted from the "
+            " process. Run in an isolated network environment.",
+            .pre_fuzz = &virtio_net_pre_fuzz,
+            .fuzz = virtio_net_fork_fuzz,},
+            "virtio-net",
+            &(QOSGraphTestOptions){.before = virtio_net_test_setup_user}
+            );
+}
+
+fuzz_target_init(register_virtio_net_fuzz_targets);