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qemu-e2k/tests/qtest/fuzz/generic_fuzz.c
Alexander Bulekov b8b52178e2 fuzz/generic-fuzz: add a limit on DMA bytes written 
As we have repplaced fork-based fuzzing, with reboots - we can no longer
use a timeout+exit() to avoid slow inputs. Libfuzzer has its own timer
that it uses to catch slow inputs, however these timeouts are usually
seconds-minutes long: more than enough to bog-down the fuzzing process.
However, I found that slow inputs often attempt to fill overly large DMA
requests. Thus, we can mitigate most timeouts by setting a cap on the
total number of DMA bytes written by an input.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
2023-02-16 23:02:46 -05:00

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/*
* 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/libqtest.h"
#include "tests/qtest/libqos/pci-pc.h"
#include "fuzz.h"
#include "string.h"
#include "exec/memory.h"
#include "exec/ramblock.h"
#include "hw/qdev-core.h"
#include "hw/pci/pci.h"
#include "hw/pci/pci_device.h"
#include "hw/boards.h"
#include "generic_fuzz_configs.h"
#include "hw/mem/sparse-mem.h"
static void pci_enum(gpointer pcidev, gpointer bus);
/*
* SEPARATOR is used to separate "operations" in the fuzz input
*/
#define SEPARATOR "FUZZ"
enum cmds {
OP_IN,
OP_OUT,
OP_READ,
OP_WRITE,
OP_PCI_READ,
OP_PCI_WRITE,
OP_DISABLE_PCI,
OP_ADD_DMA_PATTERN,
OP_CLEAR_DMA_PATTERNS,
OP_CLOCK_STEP,
};
#define USEC_IN_SEC 1000000000
#define MAX_DMA_FILL_SIZE 0x10000
#define MAX_TOTAL_DMA_SIZE 0x10000000
#define PCI_HOST_BRIDGE_CFG 0xcf8
#define PCI_HOST_BRIDGE_DATA 0xcfc
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 bool qtest_log_enabled;
size_t dma_bytes_written;
MemoryRegion *sparse_mem_mr;
/*
* A pattern used to populate a DMA region or perform a memwrite. This is
* useful for e.g. populating tables of unique addresses.
* Example {.index = 1; .stride = 2; .len = 3; .data = "\x00\x01\x02"}
* Renders as: 00 01 02 00 03 02 00 05 02 00 07 02 ...
*/
typedef struct {
uint8_t index; /* Index of a byte to increment by stride */
uint8_t stride; /* Increment each index'th byte by this amount */
size_t len;
const uint8_t *data;
} pattern;
/* Avoid filling the same DMA region between MMIO/PIO commands ? */
static bool avoid_double_fetches;
static QTestState *qts_global; /* Need a global for the DMA callback */
/*
* List of memory regions that are children of QOM objects specified by the
* user for fuzzing.
*/
static GHashTable *fuzzable_memoryregions;
static GPtrArray *fuzzable_pci_devices;
struct get_io_cb_info {
int index;
int found;
address_range result;
};
static bool get_io_address_cb(Int128 start, Int128 size,
const MemoryRegion *mr,
hwaddr offset_in_region,
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 true;
}
info->index--;
}
return false;
}
/*
* List of dma regions populated since the last fuzzing command. Used to ensure
* that we only write to each DMA address once, to avoid race conditions when
* building reproducers.
*/
static GArray *dma_regions;
static GArray *dma_patterns;
static int dma_pattern_index;
static bool pci_disabled;
/*
* Allocate a block of memory and populate it with a pattern.
*/
static void *pattern_alloc(pattern p, size_t len)
{
int i;
uint8_t *buf = g_malloc(len);
uint8_t sum = 0;
for (i = 0; i < len; ++i) {
buf[i] = p.data[i % p.len];
if ((i % p.len) == p.index) {
buf[i] += sum;
sum += p.stride;
}
}
return buf;
}
static int fuzz_memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr)
{
unsigned access_size_max = mr->ops->valid.max_access_size;
/*
* Regions are assumed to support 1-4 byte accesses unless
* otherwise specified.
*/
if (access_size_max == 0) {
access_size_max = 4;
}
/* Bound the maximum access by the alignment of the address. */
if (!mr->ops->impl.unaligned) {
unsigned align_size_max = addr & -addr;
if (align_size_max != 0 && align_size_max < access_size_max) {
access_size_max = align_size_max;
}
}
/* Don't attempt accesses larger than the maximum. */
if (l > access_size_max) {
l = access_size_max;
}
l = pow2floor(l);
return l;
}
/*
* Call-back for functions that perform DMA reads from guest memory. Confirm
* that the region has not already been populated since the last loop in
* generic_fuzz(), avoiding potential race-conditions, which we don't have
* a good way for reproducing right now.
*/
void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
{
/* Are we in the generic-fuzzer or are we using another fuzz-target? */
if (!qts_global) {
return;
}
/*
* Return immediately if:
* - We have no DMA patterns defined
* - The length of the DMA read request is zero
* - The DMA read is hitting an MR other than the machine's main RAM
* - The DMA request hits past the bounds of our RAM
*/
if (dma_patterns->len == 0
|| len == 0
|| dma_bytes_written + len > MAX_TOTAL_DMA_SIZE
|| (mr != current_machine->ram && mr != sparse_mem_mr)) {
return;
}
/*
* If we overlap with any existing dma_regions, split the range and only
* populate the non-overlapping parts.
*/
address_range region;
bool double_fetch = false;
for (int i = 0;
i < dma_regions->len && (avoid_double_fetches || qtest_log_enabled);
++i) {
region = g_array_index(dma_regions, address_range, i);
if (addr < region.addr + region.size && addr + len > region.addr) {
double_fetch = true;
if (addr < region.addr
&& avoid_double_fetches) {
fuzz_dma_read_cb(addr, region.addr - addr, mr);
}
if (addr + len > region.addr + region.size
&& avoid_double_fetches) {
fuzz_dma_read_cb(region.addr + region.size,
addr + len - (region.addr + region.size), mr);
}
return;
}
}
/* Cap the length of the DMA access to something reasonable */
len = MIN(len, MAX_DMA_FILL_SIZE);
address_range ar = {addr, len};
g_array_append_val(dma_regions, ar);
pattern p = g_array_index(dma_patterns, pattern, dma_pattern_index);
void *buf_base = pattern_alloc(p, ar.size);
void *buf = buf_base;
hwaddr l, addr1;
MemoryRegion *mr1;
while (len > 0) {
l = len;
mr1 = address_space_translate(first_cpu->as,
addr, &addr1, &l, true,
MEMTXATTRS_UNSPECIFIED);
/*
* If mr1 isn't RAM, address_space_translate doesn't update l. Use
* fuzz_memory_access_size to identify the number of bytes that it
* is safe to write without accidentally writing to another
* MemoryRegion.
*/
if (!memory_region_is_ram(mr1)) {
l = fuzz_memory_access_size(mr1, l, addr1);
}
if (memory_region_is_ram(mr1) ||
memory_region_is_romd(mr1) ||
mr1 == sparse_mem_mr) {
/* ROM/RAM case */
if (qtest_log_enabled) {
/*
* With QTEST_LOG, use a normal, slow QTest memwrite. Prefix the log
* that will be written by qtest.c with a DMA tag, so we can reorder
* the resulting QTest trace so the DMA fills precede the last PIO/MMIO
* command.
*/
fprintf(stderr, "[DMA] ");
if (double_fetch) {
fprintf(stderr, "[DOUBLE-FETCH] ");
}
fflush(stderr);
}
qtest_memwrite(qts_global, addr, buf, l);
dma_bytes_written += l;
}
len -= l;
buf += l;
addr += l;
}
g_free(buf_base);
/* Increment the index of the pattern for the next DMA access */
dma_pattern_index = (dma_pattern_index + 1) % dma_patterns->len;
}
/*
* 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;
if (result->size) {
offset = offset % result->size;
result->addr += offset;
result->size -= offset;
}
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_pci_read(QTestState *s, const unsigned char * data, size_t len)
{
enum Sizes {Byte, Word, Long, end_sizes};
struct {
uint8_t size;
uint8_t base;
uint8_t offset;
} a;
if (len < sizeof(a) || fuzzable_pci_devices->len == 0 || pci_disabled) {
return;
}
memcpy(&a, data, sizeof(a));
PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
a.base % fuzzable_pci_devices->len);
int devfn = dev->devfn;
qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
switch (a.size %= end_sizes) {
case Byte:
qtest_inb(s, PCI_HOST_BRIDGE_DATA);
break;
case Word:
qtest_inw(s, PCI_HOST_BRIDGE_DATA);
break;
case Long:
qtest_inl(s, PCI_HOST_BRIDGE_DATA);
break;
}
}
static void op_pci_write(QTestState *s, const unsigned char * data, size_t len)
{
enum Sizes {Byte, Word, Long, end_sizes};
struct {
uint8_t size;
uint8_t base;
uint8_t offset;
uint32_t value;
} a;
if (len < sizeof(a) || fuzzable_pci_devices->len == 0 || pci_disabled) {
return;
}
memcpy(&a, data, sizeof(a));
PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
a.base % fuzzable_pci_devices->len);
int devfn = dev->devfn;
qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
switch (a.size %= end_sizes) {
case Byte:
qtest_outb(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFF);
break;
case Word:
qtest_outw(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFF);
break;
case Long:
qtest_outl(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFFFFFF);
break;
}
}
static void op_add_dma_pattern(QTestState *s,
const unsigned char *data, size_t len)
{
struct {
/*
* index and stride can be used to increment the index-th byte of the
* pattern by the value stride, for each loop of the pattern.
*/
uint8_t index;
uint8_t stride;
} a;
if (len < sizeof(a) + 1) {
return;
}
memcpy(&a, data, sizeof(a));
pattern p = {a.index, a.stride, len - sizeof(a), data + sizeof(a)};
p.index = a.index % p.len;
g_array_append_val(dma_patterns, p);
return;
}
static void op_clear_dma_patterns(QTestState *s,
const unsigned char *data, size_t len)
{
g_array_set_size(dma_patterns, 0);
dma_pattern_index = 0;
}
static void op_clock_step(QTestState *s, const unsigned char *data, size_t len)
{
qtest_clock_step_next(s);
}
static void op_disable_pci(QTestState *s, const unsigned char *data, size_t len)
{
pci_disabled = true;
}
/*
* 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_PCI_READ] = op_pci_read,
[OP_PCI_WRITE] = op_pci_write,
[OP_DISABLE_PCI] = op_disable_pci,
[OP_ADD_DMA_PATTERN] = op_add_dma_pattern,
[OP_CLEAR_DMA_PATTERNS] = op_clear_dma_patterns,
[OP_CLOCK_STEP] = op_clock_step,
};
const unsigned char *cmd = Data;
const unsigned char *nextcmd;
size_t cmd_len;
uint8_t op;
op_clear_dma_patterns(s, NULL, 0);
pci_disabled = false;
dma_bytes_written = 0;
QPCIBus *pcibus = qpci_new_pc(s, NULL);
g_ptr_array_foreach(fuzzable_pci_devices, pci_enum, pcibus);
qpci_free_pc(pcibus);
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);
g_array_set_size(dma_regions, 0);
}
fuzz_reset(s);
}
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_AVOID_DOUBLE_FETCH= "
"Try to avoid racy DMA double fetch bugs? %d by default\n",
avoid_double_fetches);
exit(0);
}
static int locate_fuzz_memory_regions(Object *child, void *opaque)
{
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) {
/*
* 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)
{
GString *type_name;
GString *path_name;
char *pattern = opaque;
type_name = g_string_new(object_get_typename(child));
g_string_ascii_down(type_name);
if (g_pattern_match_simple(pattern, type_name->str)) {
/* Find and save ptrs to any child MemoryRegions */
object_child_foreach_recursive(child, locate_fuzz_memory_regions, NULL);
/*
* We matched an object. If its a PCI device, store a pointer to it so
* we can map BARs and fuzz its config space.
*/
if (object_dynamic_cast(OBJECT(child), TYPE_PCI_DEVICE)) {
/*
* Don't want duplicate pointers to the same PCIDevice, so remove
* copies of the pointer, before adding it.
*/
g_ptr_array_remove_fast(fuzzable_pci_devices, PCI_DEVICE(child));
g_ptr_array_add(fuzzable_pci_devices, PCI_DEVICE(child));
}
} else if (object_dynamic_cast(OBJECT(child), TYPE_MEMORY_REGION)) {
path_name = g_string_new(object_get_canonical_path_component(child));
g_string_ascii_down(path_name);
if (g_pattern_match_simple(pattern, path_name->str)) {
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);
}
}
g_string_free(path_name, true);
}
g_string_free(type_name, true);
return 0;
}
static void pci_enum(gpointer pcidev, gpointer bus)
{
PCIDevice *dev = pcidev;
QPCIDevice *qdev;
int i;
qdev = qpci_device_find(bus, dev->devfn);
g_assert(qdev != NULL);
for (i = 0; i < 6; i++) {
if (dev->io_regions[i].size) {
qpci_iomap(qdev, i, NULL);
}
}
qpci_device_enable(qdev);
g_free(qdev);
}
static void generic_pre_fuzz(QTestState *s)
{
GHashTableIter iter;
MemoryRegion *mr;
char **result;
GString *name_pattern;
if (!getenv("QEMU_FUZZ_OBJECTS")) {
usage();
}
if (getenv("QTEST_LOG")) {
qtest_log_enabled = 1;
}
if (getenv("QEMU_AVOID_DOUBLE_FETCH")) {
avoid_double_fetches = 1;
}
qts_global = s;
/*
* Create a special device that we can use to back DMA buffers at very
* high memory addresses
*/
sparse_mem_mr = sparse_mem_init(0, UINT64_MAX);
dma_regions = g_array_new(false, false, sizeof(address_range));
dma_patterns = g_array_new(false, false, sizeof(pattern));
fuzzable_memoryregions = g_hash_table_new(NULL, NULL);
fuzzable_pci_devices = g_ptr_array_new();
result = g_strsplit(getenv("QEMU_FUZZ_OBJECTS"), " ", -1);
for (int i = 0; result[i] != NULL; i++) {
name_pattern = g_string_new(result[i]);
/*
* Make the pattern lowercase. We do the same for all the MemoryRegion
* and Type names so the configs are case-insensitive.
*/
g_string_ascii_down(name_pattern);
printf("Matching objects by name %s\n", result[i]);
object_child_foreach_recursive(qdev_get_machine(),
locate_fuzz_objects,
name_pattern->str);
g_string_free(name_pattern, true);
}
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 0x%" PRIx64 ")\n",
object_get_canonical_path_component(&(mr->parent_obj)),
memory_region_size(mr));
}
if (!g_hash_table_size(fuzzable_memoryregions)) {
printf("No fuzzable memory regions found...\n");
exit(1);
}
}
/*
* When libfuzzer gives us two inputs to combine, return a new input with the
* following structure:
*
* Input 1 (data1)
* SEPARATOR
* Clear out the DMA Patterns
* SEPARATOR
* Disable the pci_read/write instructions
* SEPARATOR
* Input 2 (data2)
*
* The idea is to collate the core behaviors of the two inputs.
* For example:
* Input 1: maps a device's BARs, sets up three DMA patterns, and triggers
* device functionality A
* Input 2: maps a device's BARs, sets up one DMA pattern, and triggers device
* functionality B
*
* This function attempts to produce an input that:
* Ouptut: maps a device's BARs, set up three DMA patterns, triggers
* functionality A device, replaces the DMA patterns with a single
* patten, and triggers device functionality B.
*/
static size_t generic_fuzz_crossover(const uint8_t *data1, size_t size1, const
uint8_t *data2, size_t size2, uint8_t *out,
size_t max_out_size, unsigned int seed)
{
size_t copy_len = 0, size = 0;
/* Check that we have enough space for data1 and at least part of data2 */
if (max_out_size <= size1 + strlen(SEPARATOR) * 3 + 2) {
return 0;
}
/* Copy_Len in the first input */
copy_len = size1;
memcpy(out + size, data1, copy_len);
size += copy_len;
max_out_size -= copy_len;
/* Append a separator */
copy_len = strlen(SEPARATOR);
memcpy(out + size, SEPARATOR, copy_len);
size += copy_len;
max_out_size -= copy_len;
/* Clear out the DMA Patterns */
copy_len = 1;
if (copy_len) {
out[size] = OP_CLEAR_DMA_PATTERNS;
}
size += copy_len;
max_out_size -= copy_len;
/* Append a separator */
copy_len = strlen(SEPARATOR);
memcpy(out + size, SEPARATOR, copy_len);
size += copy_len;
max_out_size -= copy_len;
/* Disable PCI ops. Assume data1 took care of setting up PCI */
copy_len = 1;
if (copy_len) {
out[size] = OP_DISABLE_PCI;
}
size += copy_len;
max_out_size -= copy_len;
/* Append a separator */
copy_len = strlen(SEPARATOR);
memcpy(out + size, SEPARATOR, copy_len);
size += copy_len;
max_out_size -= copy_len;
/* Copy_Len over the second input */
copy_len = MIN(size2, max_out_size);
memcpy(out + size, data2, copy_len);
size += copy_len;
max_out_size -= copy_len;
return size;
}
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 GString *generic_fuzz_predefined_config_cmdline(FuzzTarget *t)
{
gchar *args;
const generic_fuzz_config *config;
g_assert(t->opaque);
config = t->opaque;
g_setenv("QEMU_AVOID_DOUBLE_FETCH", "1", 1);
if (config->argfunc) {
args = config->argfunc();
g_setenv("QEMU_FUZZ_ARGS", args, 1);
g_free(args);
} else {
g_assert_nonnull(config->args);
g_setenv("QEMU_FUZZ_ARGS", config->args, 1);
}
g_setenv("QEMU_FUZZ_OBJECTS", config->objects, 1);
return generic_fuzz_cmdline(t);
}
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,
.crossover = generic_fuzz_crossover
});
GString *name;
const generic_fuzz_config *config;
for (int i = 0;
i < sizeof(predefined_configs) / sizeof(generic_fuzz_config);
i++) {
config = predefined_configs + i;
name = g_string_new("generic-fuzz");
g_string_append_printf(name, "-%s", config->name);
fuzz_add_target(&(FuzzTarget){
.name = name->str,
.description = "Predefined generic-fuzz config.",
.get_init_cmdline = generic_fuzz_predefined_config_cmdline,
.pre_fuzz = generic_pre_fuzz,
.fuzz = generic_fuzz,
.crossover = generic_fuzz_crossover,
.opaque = (void *)config
});
}
}
fuzz_target_init(register_generic_fuzz_targets);
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