[PATCH v1 1/2] fuzz: add virtio-blk fuzz target

[Dima Stepanov]

The virtio-blk fuzz target sets up and fuzzes the available virtio-blk
queues. The implementation is based on two files:
  - tests/qtest/fuzz/virtio_scsi_fuzz.c
  - tests/qtest/virtio_blk_test.c

Signed-off-by: Dima Stepanov <dimastep@yandex-team.ru>
---
 tests/qtest/fuzz/meson.build       |   1 +
 tests/qtest/fuzz/virtio_blk_fuzz.c | 234 +++++++++++++++++++++++++++++++++++++
 2 files changed, 235 insertions(+)
 create mode 100644 tests/qtest/fuzz/virtio_blk_fuzz.c

diff --git a/tests/qtest/fuzz/meson.build b/tests/qtest/fuzz/meson.build
index b31ace7..3b923dc 100644
--- a/tests/qtest/fuzz/meson.build
+++ b/tests/qtest/fuzz/meson.build
@@ -5,6 +5,7 @@ specific_fuzz_ss.add(files('fuzz.c', 'fork_fuzz.c', 
'qos_fuzz.c',
 specific_fuzz_ss.add(when: 'CONFIG_I440FX', if_true: files('i440fx_fuzz.c'))
 specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: 
files('virtio_net_fuzz.c'))
 specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_SCSI', if_true: 
files('virtio_scsi_fuzz.c'))
+specific_fuzz_ss.add(files('virtio_blk_fuzz.c'))
 
 fork_fuzz = declare_dependency(
   link_args: config_host['FUZZ_EXE_LDFLAGS'].split() +
diff --git a/tests/qtest/fuzz/virtio_blk_fuzz.c 
b/tests/qtest/fuzz/virtio_blk_fuzz.c
new file mode 100644
index 0000000..623a756
--- /dev/null
+++ b/tests/qtest/fuzz/virtio_blk_fuzz.c
@@ -0,0 +1,234 @@
+/*
+ * virtio-blk Fuzzing Target
+ *
+ * Copyright Red Hat Inc., 2020
+ *
+ * Based on virtio-scsi-fuzz target.
+ *
+ * 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 "tests/qtest/libqos/libqtest.h"
+#include "tests/qtest/libqos/virtio-blk.h"
+#include "tests/qtest/libqos/virtio.h"
+#include "tests/qtest/libqos/virtio-pci.h"
+#include "standard-headers/linux/virtio_ids.h"
+#include "standard-headers/linux/virtio_pci.h"
+#include "standard-headers/linux/virtio_blk.h"
+#include "fuzz.h"
+#include "fork_fuzz.h"
+#include "qos_fuzz.h"
+
+#define TEST_IMAGE_SIZE         (64 * 1024 * 1024)
+#define PCI_SLOT                0x02
+#define PCI_FN                  0x00
+
+#define MAX_NUM_QUEUES 64
+
+/* Based on tests/qtest/virtio-blk-test.c. */
+typedef struct {
+    int num_queues;
+    QVirtQueue *vq[MAX_NUM_QUEUES + 2];
+} QVirtioBlkQueues;
+
+static QVirtioBlkQueues *qvirtio_blk_init(QVirtioDevice *dev, uint64_t mask)
+{
+    QVirtioBlkQueues *vs;
+    uint64_t features;
+
+    vs = g_new0(QVirtioBlkQueues, 1);
+
+    features = qvirtio_get_features(dev);
+    if (!mask) {
+        mask = ~((1u << VIRTIO_RING_F_INDIRECT_DESC) |
+                (1u << VIRTIO_RING_F_EVENT_IDX) |
+                (1u << VIRTIO_BLK_F_SCSI));
+    }
+    mask |= ~QVIRTIO_F_BAD_FEATURE;
+    features &= mask;
+    qvirtio_set_features(dev, features);
+
+    vs->num_queues = 1;
+    vs->vq[0] = qvirtqueue_setup(dev, fuzz_qos_alloc, 0);
+
+    qvirtio_set_driver_ok(dev);
+
+    return vs;
+}
+
+static void virtio_blk_fuzz(QTestState *s, QVirtioBlkQueues* queues,
+        const unsigned char *Data, size_t Size)
+{
+    /*
+     * Data is a sequence of random bytes. We split them up into "actions",
+     * followed by data:
+     * [vqa][dddddddd][vqa][dddd][vqa][dddddddddddd] ...
+     * The length of the data is specified by the preceding vqa.length
+     */
+    typedef struct vq_action {
+        uint8_t queue;
+        uint8_t length;
+        uint8_t write;
+        uint8_t next;
+        uint8_t kick;
+    } vq_action;
+
+    /* Keep track of the free head for each queue we interact with */
+    bool vq_touched[MAX_NUM_QUEUES + 2] = {0};
+    uint32_t free_head[MAX_NUM_QUEUES + 2];
+
+    QGuestAllocator *t_alloc = fuzz_qos_alloc;
+
+    QVirtioBlk *blk = fuzz_qos_obj;
+    QVirtioDevice *dev = blk->vdev;
+    QVirtQueue *q;
+    vq_action vqa;
+    while (Size >= sizeof(vqa)) {
+        /* Copy the action, so we can normalize length, queue and flags */
+        memcpy(&vqa, Data, sizeof(vqa));
+
+        Data += sizeof(vqa);
+        Size -= sizeof(vqa);
+
+        vqa.queue = vqa.queue % queues->num_queues;
+        /* Cap length at the number of remaining bytes in data */
+        vqa.length = vqa.length >= Size ? Size : vqa.length;
+        vqa.write = vqa.write & 1;
+        vqa.next = vqa.next & 1;
+        vqa.kick = vqa.kick & 1;
+
+        q = queues->vq[vqa.queue];
+
+        /* Copy the data into ram, and place it on the virtqueue */
+        uint64_t req_addr = guest_alloc(t_alloc, vqa.length);
+        qtest_memwrite(s, req_addr, Data, vqa.length);
+        if (vq_touched[vqa.queue] == 0) {
+            vq_touched[vqa.queue] = 1;
+            free_head[vqa.queue] = qvirtqueue_add(s, q, req_addr, vqa.length,
+                    vqa.write, vqa.next);
+        } else {
+            qvirtqueue_add(s, q, req_addr, vqa.length, vqa.write , vqa.next);
+        }
+
+        if (vqa.kick) {
+            qvirtqueue_kick(s, dev, q, free_head[vqa.queue]);
+            free_head[vqa.queue] = 0;
+        }
+        Data += vqa.length;
+        Size -= vqa.length;
+    }
+    /* In the end, kick each queue we interacted with */
+    for (int i = 0; i < MAX_NUM_QUEUES + 2; i++) {
+        if (vq_touched[i]) {
+            qvirtqueue_kick(s, dev, queues->vq[i], free_head[i]);
+        }
+    }
+}
+
+static void virtio_blk_fork_fuzz(QTestState *s,
+        const unsigned char *Data, size_t Size)
+{
+    QVirtioBlk *blk = fuzz_qos_obj;
+    static QVirtioBlkQueues *queues;
+    if (!queues) {
+        queues = qvirtio_blk_init(blk->vdev, 0);
+    }
+    if (fork() == 0) {
+        virtio_blk_fuzz(s, queues, Data, Size);
+        flush_events(s);
+        _Exit(0);
+    } else {
+        flush_events(s);
+        wait(NULL);
+    }
+}
+
+static void virtio_blk_with_flag_fuzz(QTestState *s,
+        const unsigned char *Data, size_t Size)
+{
+    QVirtioBlk *blk = fuzz_qos_obj;
+    static QVirtioBlkQueues *queues;
+
+    if (fork() == 0) {
+        if (Size >= sizeof(uint64_t)) {
+            queues = qvirtio_blk_init(blk->vdev, *(uint64_t *)Data);
+            virtio_blk_fuzz(s, queues,
+                             Data + sizeof(uint64_t), Size - sizeof(uint64_t));
+            flush_events(s);
+        }
+        _Exit(0);
+    } else {
+        flush_events(s);
+        wait(NULL);
+    }
+}
+
+static void virtio_blk_pre_fuzz(QTestState *s)
+{
+    qos_init_path(s);
+    counter_shm_init();
+}
+
+static void drive_destroy(void *path)
+{
+    unlink(path);
+    g_free(path);
+}
+
+static char *drive_create(void)
+{
+    int fd, ret;
+    char *t_path = g_strdup("/tmp/qtest.XXXXXX");
+
+    /* Create a temporary raw image */
+    fd = mkstemp(t_path);
+    g_assert_cmpint(fd, >=, 0);
+    ret = ftruncate(fd, TEST_IMAGE_SIZE);
+    g_assert_cmpint(ret, ==, 0);
+    close(fd);
+
+    g_test_queue_destroy(drive_destroy, t_path);
+    return t_path;
+}
+
+static void *virtio_blk_test_setup(GString *cmd_line, void *arg)
+{
+    char *tmp_path = drive_create();
+
+    g_string_append_printf(cmd_line,
+                           " -drive if=none,id=drive0,file=%s,"
+                           "format=raw,auto-read-only=off ",
+                           tmp_path);
+
+    return arg;
+}
+
+static void register_virtio_blk_fuzz_targets(void)
+{
+    fuzz_add_qos_target(&(FuzzTarget){
+                .name = "virtio-blk-fuzz",
+                .description = "Fuzz the virtio-blk virtual queues, forking "
+                                "for each fuzz run",
+                .pre_vm_init = &counter_shm_init,
+                .pre_fuzz = &virtio_blk_pre_fuzz,
+                .fuzz = virtio_blk_fork_fuzz,},
+                "virtio-blk",
+                &(QOSGraphTestOptions){.before = virtio_blk_test_setup}
+                );
+
+    fuzz_add_qos_target(&(FuzzTarget){
+                .name = "virtio-blk-flags-fuzz",
+                .description = "Fuzz the virtio-blk virtual queues, forking "
+                "for each fuzz run (also fuzzes the virtio flags)",
+                .pre_vm_init = &counter_shm_init,
+                .pre_fuzz = &virtio_blk_pre_fuzz,
+                .fuzz = virtio_blk_with_flag_fuzz,},
+                "virtio-blk",
+                &(QOSGraphTestOptions){.before = virtio_blk_test_setup}
+                );
+}
+
+fuzz_target_init(register_virtio_blk_fuzz_targets);
-- 
2.7.4