new file mode 100644
@@ -0,0 +1,512 @@
+/*
+ * Generic Virtual-Device Fuzzing Target
+ *
+ * Copyright Red Hat Inc., 2020
+ *
+ * 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 <wordexp.h>
+
+#include "hw/core/cpu.h"
+#include "tests/qtest/libqos/libqtest.h"
+#include "fuzz.h"
+#include "fork_fuzz.h"
+#include "exec/address-spaces.h"
+#include "string.h"
+#include "exec/memory.h"
+#include "exec/ramblock.h"
+#include "exec/address-spaces.h"
+#include "hw/qdev-core.h"
+
+/*
+ * SEPARATOR is used to separate "operations" in the fuzz input
+ */
+#define SEPARATOR "FUZZ"
+
+enum cmds {
+ OP_IN,
+ OP_OUT,
+ OP_READ,
+ OP_WRITE,
+ OP_CLOCK_STEP,
+};
+
+#define DEFAULT_TIMEOUT_US 100000
+#define USEC_IN_SEC 1000000000
+
+typedef struct {
+ ram_addr_t addr;
+ ram_addr_t size; /* The number of bytes until the end of the I/O region */
+} address_range;
+
+static useconds_t timeout = DEFAULT_TIMEOUT_US;
+
+static bool qtest_log_enabled;
+
+/*
+ * List of memory regions that are children of QOM objects specified by the
+ * user for fuzzing.
+ */
+static GHashTable *fuzzable_memoryregions;
+
+struct get_io_cb_info {
+ int index;
+ int found;
+ address_range result;
+};
+
+static int get_io_address_cb(Int128 start, Int128 size,
+ const MemoryRegion *mr, void *opaque) {
+ struct get_io_cb_info *info = opaque;
+ if (g_hash_table_lookup(fuzzable_memoryregions, mr)) {
+ if (info->index == 0) {
+ info->result.addr = (ram_addr_t)start;
+ info->result.size = (ram_addr_t)size;
+ info->found = 1;
+ return 1;
+ }
+ info->index--;
+ }
+ return 0;
+}
+
+/*
+ * Here we want to convert a fuzzer-provided [io-region-index, offset] to
+ * a physical address. To do this, we iterate over all of the matched
+ * MemoryRegions. Check whether each region exists within the particular io
+ * space. Return the absolute address of the offset within the index'th region
+ * that is a subregion of the io_space and the distance until the end of the
+ * memory region.
+ */
+static bool get_io_address(address_range *result, AddressSpace *as,
+ uint8_t index,
+ uint32_t offset) {
+ FlatView *view;
+ view = as->current_map;
+ g_assert(view);
+ struct get_io_cb_info cb_info = {};
+
+ cb_info.index = index;
+
+ /*
+ * Loop around the FlatView until we match "index" number of
+ * fuzzable_memoryregions, or until we know that there are no matching
+ * memory_regions.
+ */
+ do {
+ flatview_for_each_range(view, get_io_address_cb , &cb_info);
+ } while (cb_info.index != index && !cb_info.found);
+
+ *result = cb_info.result;
+ return cb_info.found;
+}
+static bool get_pio_address(address_range *result,
+ uint8_t index, uint16_t offset)
+{
+ /*
+ * PIO BARs can be set past the maximum port address (0xFFFF). Thus, result
+ * can contain an addr that extends past the PIO space. When we pass this
+ * address to qtest_in/qtest_out, it is cast to a uint16_t, so we might end
+ * up fuzzing a completely different MemoryRegion/Device. Therefore, check
+ * that the address here is within the PIO space limits.
+ */
+ bool found = get_io_address(result, &address_space_io, index, offset);
+ return result->addr <= 0xFFFF ? found : false;
+}
+static bool get_mmio_address(address_range *result,
+ uint8_t index, uint32_t offset)
+{
+ return get_io_address(result, &address_space_memory, index, offset);
+}
+
+static void op_in(QTestState *s, const unsigned char * data, size_t len)
+{
+ enum Sizes {Byte, Word, Long, end_sizes};
+ struct {
+ uint8_t size;
+ uint8_t base;
+ uint16_t offset;
+ } a;
+ address_range abs;
+
+ if (len < sizeof(a)) {
+ return;
+ }
+ memcpy(&a, data, sizeof(a));
+ if (get_pio_address(&abs, a.base, a.offset) == 0) {
+ return;
+ }
+
+ switch (a.size %= end_sizes) {
+ case Byte:
+ qtest_inb(s, abs.addr);
+ break;
+ case Word:
+ if (abs.size >= 2) {
+ qtest_inw(s, abs.addr);
+ }
+ break;
+ case Long:
+ if (abs.size >= 4) {
+ qtest_inl(s, abs.addr);
+ }
+ break;
+ }
+}
+
+static void op_out(QTestState *s, const unsigned char * data, size_t len)
+{
+ enum Sizes {Byte, Word, Long, end_sizes};
+ struct {
+ uint8_t size;
+ uint8_t base;
+ uint16_t offset;
+ uint32_t value;
+ } a;
+ address_range abs;
+
+ if (len < sizeof(a)) {
+ return;
+ }
+ memcpy(&a, data, sizeof(a));
+
+ if (get_pio_address(&abs, a.base, a.offset) == 0) {
+ return;
+ }
+
+ switch (a.size %= end_sizes) {
+ case Byte:
+ qtest_outb(s, abs.addr, a.value & 0xFF);
+ break;
+ case Word:
+ if (abs.size >= 2) {
+ qtest_outw(s, abs.addr, a.value & 0xFFFF);
+ }
+ break;
+ case Long:
+ if (abs.size >= 4) {
+ qtest_outl(s, abs.addr, a.value);
+ }
+ break;
+ }
+}
+
+static void op_read(QTestState *s, const unsigned char * data, size_t len)
+{
+ enum Sizes {Byte, Word, Long, Quad, end_sizes};
+ struct {
+ uint8_t size;
+ uint8_t base;
+ uint32_t offset;
+ } a;
+ address_range abs;
+
+ if (len < sizeof(a)) {
+ return;
+ }
+ memcpy(&a, data, sizeof(a));
+
+ if (get_mmio_address(&abs, a.base, a.offset) == 0) {
+ return;
+ }
+
+ switch (a.size %= end_sizes) {
+ case Byte:
+ qtest_readb(s, abs.addr);
+ break;
+ case Word:
+ if (abs.size >= 2) {
+ qtest_readw(s, abs.addr);
+ }
+ break;
+ case Long:
+ if (abs.size >= 4) {
+ qtest_readl(s, abs.addr);
+ }
+ break;
+ case Quad:
+ if (abs.size >= 8) {
+ qtest_readq(s, abs.addr);
+ }
+ break;
+ }
+}
+
+static void op_write(QTestState *s, const unsigned char * data, size_t len)
+{
+ enum Sizes {Byte, Word, Long, Quad, end_sizes};
+ struct {
+ uint8_t size;
+ uint8_t base;
+ uint32_t offset;
+ uint64_t value;
+ } a;
+ address_range abs;
+
+ if (len < sizeof(a)) {
+ return;
+ }
+ memcpy(&a, data, sizeof(a));
+
+ if (get_mmio_address(&abs, a.base, a.offset) == 0) {
+ return;
+ }
+
+ switch (a.size %= end_sizes) {
+ case Byte:
+ qtest_writeb(s, abs.addr, a.value & 0xFF);
+ break;
+ case Word:
+ if (abs.size >= 2) {
+ qtest_writew(s, abs.addr, a.value & 0xFFFF);
+ }
+ break;
+ case Long:
+ if (abs.size >= 4) {
+ qtest_writel(s, abs.addr, a.value & 0xFFFFFFFF);
+ }
+ break;
+ case Quad:
+ if (abs.size >= 8) {
+ qtest_writeq(s, abs.addr, a.value);
+ }
+ break;
+ }
+}
+static void op_clock_step(QTestState *s, const unsigned char *data, size_t len)
+{
+ qtest_clock_step_next(s);
+}
+
+static void handle_timeout(int sig)
+{
+ if (qtest_log_enabled) {
+ fprintf(stderr, "[Timeout]\n");
+ fflush(stderr);
+ }
+ _Exit(0);
+}
+
+/*
+ * Here, we interpret random bytes from the fuzzer, as a sequence of commands.
+ * Some commands can be variable-width, so we use a separator, SEPARATOR, to
+ * specify the boundaries between commands. SEPARATOR is used to separate
+ * "operations" in the fuzz input. Why use a separator, instead of just using
+ * the operations' length to identify operation boundaries?
+ * 1. This is a simple way to support variable-length operations
+ * 2. This adds "stability" to the input.
+ * For example take the input "AbBcgDefg", where there is no separator and
+ * Opcodes are capitalized.
+ * Simply, by removing the first byte, we end up with a very different
+ * sequence:
+ * BbcGdefg...
+ * By adding a separator, we avoid this problem:
+ * Ab SEP Bcg SEP Defg -> B SEP Bcg SEP Defg
+ * Since B uses two additional bytes as operands, the first "B" will be
+ * ignored. The fuzzer actively tries to reduce inputs, so such unused
+ * bytes are likely to be pruned, eventually.
+ *
+ * SEPARATOR is trivial for the fuzzer to discover when using ASan. Optionally,
+ * SEPARATOR can be manually specified as a dictionary value (see libfuzzer's
+ * -dict), though this should not be necessary.
+ *
+ * As a result, the stream of bytes is converted into a sequence of commands.
+ * In a simplified example where SEPARATOR is 0xFF:
+ * 00 01 02 FF 03 04 05 06 FF 01 FF ...
+ * becomes this sequence of commands:
+ * 00 01 02 -> op00 (0102) -> in (0102, 2)
+ * 03 04 05 06 -> op03 (040506) -> write (040506, 3)
+ * 01 -> op01 (-,0) -> out (-,0)
+ * ...
+ *
+ * Note here that it is the job of the individual opcode functions to check
+ * that enough data was provided. I.e. in the last command out (,0), out needs
+ * to check that there is not enough data provided to select an address/value
+ * for the operation.
+ */
+static void generic_fuzz(QTestState *s, const unsigned char *Data, size_t Size)
+{
+ void (*ops[]) (QTestState *s, const unsigned char* , size_t) = {
+ [OP_IN] = op_in,
+ [OP_OUT] = op_out,
+ [OP_READ] = op_read,
+ [OP_WRITE] = op_write,
+ [OP_CLOCK_STEP] = op_clock_step,
+ };
+ const unsigned char *cmd = Data;
+ const unsigned char *nextcmd;
+ size_t cmd_len;
+ uint8_t op;
+
+ if (fork() == 0) {
+ /*
+ * Sometimes the fuzzer will find inputs that take quite a long time to
+ * process. Often times, these inputs do not result in new coverage.
+ * Even if these inputs might be interesting, they can slow down the
+ * fuzzer, overall. Set a timeout to avoid hurting performance, too much
+ */
+ if (timeout) {
+ struct sigaction sact;
+ struct itimerval timer;
+
+ sigemptyset(&sact.sa_mask);
+ sact.sa_flags = SA_NODEFER;
+ sact.sa_handler = handle_timeout;
+ sigaction(SIGALRM, &sact, NULL);
+
+ memset(&timer, 0, sizeof(timer));
+ timer.it_value.tv_sec = timeout / USEC_IN_SEC;
+ timer.it_value.tv_usec = timeout % USEC_IN_SEC;
+ setitimer(ITIMER_VIRTUAL, &timer, NULL);
+ }
+
+ while (cmd && Size) {
+ /* Get the length until the next command or end of input */
+ nextcmd = memmem(cmd, Size, SEPARATOR, strlen(SEPARATOR));
+ cmd_len = nextcmd ? nextcmd - cmd : Size;
+
+ if (cmd_len > 0) {
+ /* Interpret the first byte of the command as an opcode */
+ op = *cmd % (sizeof(ops) / sizeof((ops)[0]));
+ ops[op](s, cmd + 1, cmd_len - 1);
+
+ /* Run the main loop */
+ flush_events(s);
+ }
+ /* Advance to the next command */
+ cmd = nextcmd ? nextcmd + sizeof(SEPARATOR) - 1 : nextcmd;
+ Size = Size - (cmd_len + sizeof(SEPARATOR) - 1);
+ }
+ _Exit(0);
+ } else {
+ flush_events(s);
+ wait(0);
+ }
+}
+
+static void usage(void)
+{
+ printf("Please specify the following environment variables:\n");
+ printf("QEMU_FUZZ_ARGS= the command line arguments passed to qemu\n");
+ printf("QEMU_FUZZ_OBJECTS= "
+ "a space separated list of QOM type names for objects to fuzz\n");
+ printf("Optionally: QEMU_FUZZ_TIMEOUT= Specify a custom timeout (us). "
+ "0 to disable. %d by default\n", timeout);
+ exit(0);
+}
+
+static int locate_fuzz_memory_regions(Object *child, void *opaque)
+{
+ const char *name;
+ MemoryRegion *mr;
+ if (object_dynamic_cast(child, TYPE_MEMORY_REGION)) {
+ mr = MEMORY_REGION(child);
+ if ((memory_region_is_ram(mr) ||
+ memory_region_is_ram_device(mr) ||
+ memory_region_is_rom(mr)) == false) {
+ name = object_get_canonical_path_component(child);
+ /*
+ * We don't want duplicate pointers to the same MemoryRegion, so
+ * try to remove copies of the pointer, before adding it.
+ */
+ g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
+ }
+ }
+ return 0;
+}
+static int locate_fuzz_objects(Object *child, void *opaque)
+{
+ char *pattern = opaque;
+ if (g_pattern_match_simple(pattern, object_get_typename(child))) {
+ /* Find and save ptrs to any child MemoryRegions */
+ object_child_foreach_recursive(child, locate_fuzz_memory_regions, NULL);
+
+ } else if (object_dynamic_cast(OBJECT(child), TYPE_MEMORY_REGION)) {
+ if (g_pattern_match_simple(pattern,
+ object_get_canonical_path_component(child))) {
+ MemoryRegion *mr;
+ mr = MEMORY_REGION(child);
+ if ((memory_region_is_ram(mr) ||
+ memory_region_is_ram_device(mr) ||
+ memory_region_is_rom(mr)) == false) {
+ g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
+ }
+ }
+ }
+ return 0;
+}
+
+static void generic_pre_fuzz(QTestState *s)
+{
+ GHashTableIter iter;
+ MemoryRegion *mr;
+ char **result;
+
+ if (!getenv("QEMU_FUZZ_OBJECTS")) {
+ usage();
+ }
+ if (getenv("QTEST_LOG")) {
+ qtest_log_enabled = 1;
+ }
+ if (getenv("QEMU_FUZZ_TIMEOUT")) {
+ timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0);
+ }
+
+ fuzzable_memoryregions = g_hash_table_new(NULL, NULL);
+
+ result = g_strsplit(getenv("QEMU_FUZZ_OBJECTS"), " ", -1);
+ for (int i = 0; result[i] != NULL; i++) {
+ printf("Matching objects by name %s\n", result[i]);
+ object_child_foreach_recursive(qdev_get_machine(),
+ locate_fuzz_objects,
+ result[i]);
+ }
+ g_strfreev(result);
+ printf("This process will try to fuzz the following MemoryRegions:\n");
+
+ g_hash_table_iter_init(&iter, fuzzable_memoryregions);
+ while (g_hash_table_iter_next(&iter, (gpointer)&mr, NULL)) {
+ printf(" * %s (size %lx)\n",
+ object_get_canonical_path_component(&(mr->parent_obj)),
+ (uint64_t)mr->size);
+ }
+
+ if (!g_hash_table_size(fuzzable_memoryregions)) {
+ printf("No fuzzable memory regions found...\n");
+ exit(1);
+ }
+
+ counter_shm_init();
+}
+
+static GString *generic_fuzz_cmdline(FuzzTarget *t)
+{
+ GString *cmd_line = g_string_new(TARGET_NAME);
+ if (!getenv("QEMU_FUZZ_ARGS")) {
+ usage();
+ }
+ g_string_append_printf(cmd_line, " -display none \
+ -machine accel=qtest, \
+ -m 512M %s ", getenv("QEMU_FUZZ_ARGS"));
+ return cmd_line;
+}
+
+static void register_generic_fuzz_targets(void)
+{
+ fuzz_add_target(&(FuzzTarget){
+ .name = "generic-fuzz",
+ .description = "Fuzz based on any qemu command-line args. ",
+ .get_init_cmdline = generic_fuzz_cmdline,
+ .pre_fuzz = generic_pre_fuzz,
+ .fuzz = generic_fuzz,
+ });
+}
+
+fuzz_target_init(register_generic_fuzz_targets);
@@ -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('generic_fuzz.c'))
fork_fuzz = declare_dependency(
link_args: config_host['FUZZ_EXE_LDFLAGS'].split() +
This is a generic fuzzer designed to fuzz a virtual device's MemoryRegions, as long as they exist within the Memory or Port IO (if it exists) AddressSpaces. The fuzzer's input is interpreted into a sequence of qtest commands (outb, readw, etc). The interpreted commands are separated by a magic seaparator, which should be easy for the fuzzer to guess. Without ASan, the separator can be specified as a "dictionary value" using the -dict argument (see libFuzzer documentation). Signed-off-by: Alexander Bulekov <alxndr@bu.edu> --- tests/qtest/fuzz/generic_fuzz.c | 512 ++++++++++++++++++++++++++++++++ tests/qtest/fuzz/meson.build | 1 + 2 files changed, 513 insertions(+) create mode 100644 tests/qtest/fuzz/generic_fuzz.c