[PATCH v4 19/20] fuzz: add virtio-net fuzz target

["Oleinik, Alexander" <alxndr@bu.edu>]

From: Alexander Oleinik <alxndr@bu.edu>

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 Oleinik <alxndr@bu.edu>
---
 tests/fuzz/Makefile.include  |   1 +
 tests/fuzz/virtio_net_fuzz.c | 123 +++++++++++++++++++++++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 tests/fuzz/virtio_net_fuzz.c

diff --git a/tests/fuzz/Makefile.include b/tests/fuzz/Makefile.include
index 37d6821bee..f1d9b46b1c 100644
--- a/tests/fuzz/Makefile.include
+++ b/tests/fuzz/Makefile.include
@@ -6,5 +6,6 @@ fuzz-obj-y += tests/fuzz/fork_fuzz.o
 fuzz-obj-y += tests/fuzz/qos_fuzz.o
 
 fuzz-obj-y += tests/fuzz/i440fx_fuzz.o
+fuzz-obj-y += tests/fuzz/virtio_net_fuzz.o
 
 FUZZ_LDFLAGS += -Xlinker -T$(SRC_PATH)/tests/fuzz/fork_fuzz.ld
diff --git a/tests/fuzz/virtio_net_fuzz.c b/tests/fuzz/virtio_net_fuzz.c
new file mode 100644
index 0000000000..0543cfd32a
--- /dev/null
+++ b/tests/fuzz/virtio_net_fuzz.c
@@ -0,0 +1,123 @@
+/*
+ * 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 "fuzz.h"
+#include "fork_fuzz.h"
+#include "qos_fuzz.h"
+#include "tests/libqtest.h"
+#include "tests/libqos/virtio-net.h"
+
+
+static void virtio_net_fuzz_multi(QTestState *s,
+        const unsigned char *Data, size_t Size)
+{
+    typedef struct vq_action {
+        uint8_t queue;
+        uint8_t length;
+        uint8_t write;
+        uint8_t next;
+        bool kick;
+    } vq_action;
+
+    uint64_t req_addr[10];
+    int reqi = 0;
+    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;
+    int iters = 0;
+    while (true) {
+        if (Size < sizeof(vqa)) {
+            break;
+        }
+        memcpy(&vqa, Data, sizeof(vqa));
+        vqa = *((vq_action *)Data);
+        Data += sizeof(vqa);
+        Size -= sizeof(vqa);
+
+        q = net_if->queues[vqa.queue % 3];
+
+        vqa.length = vqa.length >= Size ? Size :  vqa.length;
+
+        req_addr[reqi] = guest_alloc(t_alloc, vqa.length);
+        qtest_memwrite(s, req_addr[reqi], Data, vqa.length);
+        if (iters == 0) {
+            free_head = qvirtqueue_add(s, q, req_addr[reqi], vqa.length,
+                    vqa.write, vqa.next);
+        } else {
+            qvirtqueue_add(s, q,
+                    req_addr[reqi], vqa.length, vqa.write , vqa.next);
+        }
+        iters++;
+        reqi++;
+        if (iters == 10) {
+            break;
+        }
+        Data += vqa.length;
+        Size -= vqa.length;
+    }
+    if (iters) {
+        qvirtqueue_kick(s, dev, q, free_head);
+        qtest_clock_step_next(s);
+        for (int i = 0; i < reqi; i++) {
+            guest_free(t_alloc, req_addr[i]);
+        }
+    }
+}
+
+static int *sv;
+
+static void *virtio_net_test_setup_socket(GString *cmd_line, void *arg)
+{
+    if (!sv) {
+        sv = g_new(int, 2);
+        int ret = socketpair(PF_UNIX, SOCK_STREAM, 0, sv);
+        fcntl(sv[0], F_SETFL, O_NONBLOCK);
+        g_assert_cmpint(ret, !=, -1);
+    }
+    g_string_append_printf(cmd_line, " -netdev socket,fd=%d,id=hs0 ", sv[1]);
+    return arg;
+}
+
+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);
+        flush_events(s);
+        _Exit(0);
+    } else {
+        wait(NULL);
+    }
+}
+
+static void register_virtio_net_fuzz_targets(void)
+{
+    fuzz_add_qos_target(&(FuzzTarget){
+                .name = "virtio-net-fork-fuzz",
+                .description = "Fuzz the virtio-net virtual queues, forking"
+                                "for each fuzz run",
+                .pre_vm_init = &counter_shm_init,
+                .pre_fuzz = &qos_init_path,
+                .fuzz = virtio_net_fork_fuzz,},
+                "virtio-net",
+                &(QOSGraphTestOptions){.before = virtio_net_test_setup_socket}
+                );
+}
+
+fuzz_target_init(register_virtio_net_fuzz_targets);
-- 
2.23.0