Message ID | 20200723033933.21883-3-alxndr@bu.edu (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | Add a General Virtual Device Fuzzer | expand |
On 200722 2339, Alexander Bulekov wrote: > 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/Makefile.include | 1 + > tests/qtest/fuzz/general_fuzz.c | 467 ++++++++++++++++++++++++++++++ > 2 files changed, 468 insertions(+) > create mode 100644 tests/qtest/fuzz/general_fuzz.c > > diff --git a/tests/qtest/fuzz/Makefile.include b/tests/qtest/fuzz/Makefile.include > index 5bde793bf2..854322efb6 100644 > --- a/tests/qtest/fuzz/Makefile.include > +++ b/tests/qtest/fuzz/Makefile.include > @@ -11,6 +11,7 @@ fuzz-obj-y += tests/qtest/fuzz/qtest_wrappers.o > fuzz-obj-$(CONFIG_PCI_I440FX) += tests/qtest/fuzz/i440fx_fuzz.o > fuzz-obj-$(CONFIG_VIRTIO_NET) += tests/qtest/fuzz/virtio_net_fuzz.o > fuzz-obj-$(CONFIG_SCSI) += tests/qtest/fuzz/virtio_scsi_fuzz.o > +fuzz-obj-y += tests/qtest/fuzz/general_fuzz.o > > FUZZ_CFLAGS += -I$(SRC_PATH)/tests -I$(SRC_PATH)/tests/qtest > > diff --git a/tests/qtest/fuzz/general_fuzz.c b/tests/qtest/fuzz/general_fuzz.c > new file mode 100644 > index 0000000000..fd92cc5bdf > --- /dev/null > +++ b/tests/qtest/fuzz/general_fuzz.c > @@ -0,0 +1,467 @@ > +/* > + * General 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 "cpu.h" > +#include "tests/qtest/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" > + > +/* > + * CMD_SEP is a random 32-bit value used to separate "commands" in the fuzz > + * input > + */ > +#define CMD_SEP "\x84\x05\x5C\x5E" > +#define DEFAULT_TIMEOUT_US 100000 > + > +typedef struct { > + size_t addr; > + size_t len; /* The number of bytes until the end of the I/O region */ > +} address_range; > + > +static useconds_t timeout = 100000; > +/* > + * List of memory regions that are children of QOM objects specified by the > + * user for fuzzing. > + */ > +static GPtrArray *fuzzable_memoryregions; > +/* > + * 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, > + MemoryRegion *io_space, > + uint8_t index, > + uint32_t offset) { > + MemoryRegion *mr, *root; > + index = index % fuzzable_memoryregions->len; > + int candidate_regions = 0; > + int i = 0; > + int ind = index; > + size_t abs_addr; > + > + while (ind >= 0 && fuzzable_memoryregions->len) { > + *result = (address_range){0, 0}; > + mr = g_ptr_array_index(fuzzable_memoryregions, i); > + if (mr->enabled) { > + abs_addr = mr->addr; > + for (root = mr; root->container; ) { > + root = root->container; > + abs_addr += root->addr; > + } > + /* > + * Only consider the region if it is rooted at the io_space we want > + */ > + if (root == io_space) { Theres a problem here. This finds an aboslute address for an index + offset in our fuzzable_memory_regions array, but doesn't check that the MemoryRegion has the highest priority for that address. I think the way to solve this is to do the opposite address_space_translate and ensure that the MemoryRegion* we get back is the same MemoryRegion* that is in our fuzzable_memory_regions array. Only noticed this as I was trying to fuzz an audio device and saw that by fuzzing the device's PCI space the fuzzer would set the BAR over an existing higher-priority device and the fuzzer was exercising code for that device. -Alex > + ind--; > + candidate_regions++; > + result->addr = abs_addr + (offset % mr->size); > + result->len = mr->size - (offset % mr->size); > + } > + } > + ++i; > + /* Loop around */ > + if (i == fuzzable_memoryregions->len) { > + /* No enabled regions in our io_space? */ > + if (candidate_regions == 0) { > + break; > + } > + i = 0; > + } > + } > + return candidate_regions != 0; > +} > +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 success = get_io_address(result, get_system_io(), index, offset); > + return success && result->addr <= 0xFFFF; > +} > +static bool get_mmio_address(address_range *result, > + uint8_t index, uint32_t offset) > +{ > + return get_io_address(result, get_system_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.len >= 2) { > + qtest_inw(s, abs.addr); > + } > + break; > + case Long: > + if (abs.len >= 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.len >= 2) { > + qtest_outw(s, abs.addr, a.value & 0xFFFF); > + } > + break; > + case Long: > + if (abs.len >= 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.len >= 2) { > + qtest_readw(s, abs.addr); > + } > + break; > + case Long: > + if (abs.len >= 4) { > + qtest_readl(s, abs.addr); > + } > + break; > + case Quad: > + if (abs.len >= 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.len >= 2) { > + qtest_writew(s, abs.addr, a.value & 0xFFFF); > + } > + break; > + case Long: > + if (abs.len >= 4) { > + qtest_writel(s, abs.addr, a.value & 0xFFFFFFFF); > + } > + break; > + case Quad: > + if (abs.len >= 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 (getenv("QTEST_LOG")) { > + fprintf(stderr, "[Timeout]\n"); > + fflush(stderr); > + } > + _Exit(0); > +} > + > +/* > + * Here, we interpret random bytes from the fuzzer, as a sequence of commands. > + * Our commands are variable-width, so we use a separator, CMD_SEP, to specify > + * the boundaries between commands. This is just a random 32-bit value, which > + * is easily identified by libfuzzer+AddressSanitizer, as long as we use > + * memmem. It can also be included in the fuzzer's dictionary. More details > + * here: > + * https://github.com/google/fuzzing/blob/master/docs/split-inputs.md > + * > + * As a result, the stream of bytes is converted into a sequence of commands. > + * In a simplified example where CMD_SEP 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 general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) > +{ > + void (*ops[]) (QTestState *s, const unsigned char* , size_t) = { > + op_in, > + op_out, > + op_read, > + op_write, > + 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; > + sigemptyset(&sact.sa_mask); > + sact.sa_flags = 0; > + sact.sa_handler = handle_timeout; > + sigaction(SIGALRM, &sact, NULL); > + ualarm(timeout, 0); > + } > + > + while (cmd && Size) { > + /* Get the length until the next command or end of input */ > + nextcmd = memmem(cmd, Size, CMD_SEP, strlen(CMD_SEP)); > + 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(CMD_SEP) - 1 : nextcmd; > + Size = Size - (cmd_len + sizeof(CMD_SEP) - 1); > + } > + _Exit(0); > + } else { > + flush_events(s); > + wait(NULL); > + } > +} > + > +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) || > + memory_region_is_romd(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_ptr_array_remove_fast(fuzzable_memoryregions, mr); > + g_ptr_array_add(fuzzable_memoryregions, mr); > + } > + } > + return 0; > +} > +static int locate_fuzz_objects(Object *child, void *opaque) > +{ > + char *pattern = opaque; > + if (g_pattern_match_simple(pattern, object_get_typename(child))) { > + printf("Matched Object by Type: %s\n", 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) || > + memory_region_is_romd(mr)) == false) { > + g_ptr_array_remove_fast(fuzzable_memoryregions, mr); > + g_ptr_array_add(fuzzable_memoryregions, mr); > + } > + } > + } > + return 0; > +} > + > +static void general_pre_fuzz(QTestState *s) > +{ > + if (!getenv("QEMU_FUZZ_OBJECTS")) { > + usage(); > + } > + if (getenv("QEMU_FUZZ_TIMEOUT")) { > + timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0); > + } > + > + fuzzable_memoryregions = g_ptr_array_new(); > + wordexp_t result; > + wordexp(getenv("QEMU_FUZZ_OBJECTS"), &result, 0); > + for (int i = 0; i < result.we_wordc; i++) { > + object_child_foreach_recursive(qdev_get_machine(), > + locate_fuzz_objects, > + result.we_wordv[i]); > + } > + > + printf("This process will try to fuzz the following MemoryRegions:\n"); > + for (int i = 0; i < fuzzable_memoryregions->len; i++) { > + MemoryRegion *mr; > + mr = g_ptr_array_index(fuzzable_memoryregions, i); > + printf(" * %s (size %lx)\n", > + object_get_canonical_path_component(&(mr->parent_obj)), > + mr->addr); > + } > + counter_shm_init(); > +} > +static GString *general_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 64 %s ", getenv("QEMU_FUZZ_ARGS")); > + return cmd_line; > +} > + > +static void register_general_fuzz_targets(void) > +{ > + fuzz_add_target(&(FuzzTarget){ > + .name = "general-fuzz", > + .description = "Fuzz based on any qemu command-line args. ", > + .get_init_cmdline = general_fuzz_cmdline, > + .pre_fuzz = general_pre_fuzz, > + .fuzz = general_fuzz}); > +} > + > +fuzz_target_init(register_general_fuzz_targets); > -- > 2.27.0 >
diff --git a/tests/qtest/fuzz/Makefile.include b/tests/qtest/fuzz/Makefile.include index 5bde793bf2..854322efb6 100644 --- a/tests/qtest/fuzz/Makefile.include +++ b/tests/qtest/fuzz/Makefile.include @@ -11,6 +11,7 @@ fuzz-obj-y += tests/qtest/fuzz/qtest_wrappers.o fuzz-obj-$(CONFIG_PCI_I440FX) += tests/qtest/fuzz/i440fx_fuzz.o fuzz-obj-$(CONFIG_VIRTIO_NET) += tests/qtest/fuzz/virtio_net_fuzz.o fuzz-obj-$(CONFIG_SCSI) += tests/qtest/fuzz/virtio_scsi_fuzz.o +fuzz-obj-y += tests/qtest/fuzz/general_fuzz.o FUZZ_CFLAGS += -I$(SRC_PATH)/tests -I$(SRC_PATH)/tests/qtest diff --git a/tests/qtest/fuzz/general_fuzz.c b/tests/qtest/fuzz/general_fuzz.c new file mode 100644 index 0000000000..fd92cc5bdf --- /dev/null +++ b/tests/qtest/fuzz/general_fuzz.c @@ -0,0 +1,467 @@ +/* + * General 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 "cpu.h" +#include "tests/qtest/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" + +/* + * CMD_SEP is a random 32-bit value used to separate "commands" in the fuzz + * input + */ +#define CMD_SEP "\x84\x05\x5C\x5E" +#define DEFAULT_TIMEOUT_US 100000 + +typedef struct { + size_t addr; + size_t len; /* The number of bytes until the end of the I/O region */ +} address_range; + +static useconds_t timeout = 100000; +/* + * List of memory regions that are children of QOM objects specified by the + * user for fuzzing. + */ +static GPtrArray *fuzzable_memoryregions; +/* + * 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, + MemoryRegion *io_space, + uint8_t index, + uint32_t offset) { + MemoryRegion *mr, *root; + index = index % fuzzable_memoryregions->len; + int candidate_regions = 0; + int i = 0; + int ind = index; + size_t abs_addr; + + while (ind >= 0 && fuzzable_memoryregions->len) { + *result = (address_range){0, 0}; + mr = g_ptr_array_index(fuzzable_memoryregions, i); + if (mr->enabled) { + abs_addr = mr->addr; + for (root = mr; root->container; ) { + root = root->container; + abs_addr += root->addr; + } + /* + * Only consider the region if it is rooted at the io_space we want + */ + if (root == io_space) { + ind--; + candidate_regions++; + result->addr = abs_addr + (offset % mr->size); + result->len = mr->size - (offset % mr->size); + } + } + ++i; + /* Loop around */ + if (i == fuzzable_memoryregions->len) { + /* No enabled regions in our io_space? */ + if (candidate_regions == 0) { + break; + } + i = 0; + } + } + return candidate_regions != 0; +} +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 success = get_io_address(result, get_system_io(), index, offset); + return success && result->addr <= 0xFFFF; +} +static bool get_mmio_address(address_range *result, + uint8_t index, uint32_t offset) +{ + return get_io_address(result, get_system_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.len >= 2) { + qtest_inw(s, abs.addr); + } + break; + case Long: + if (abs.len >= 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.len >= 2) { + qtest_outw(s, abs.addr, a.value & 0xFFFF); + } + break; + case Long: + if (abs.len >= 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.len >= 2) { + qtest_readw(s, abs.addr); + } + break; + case Long: + if (abs.len >= 4) { + qtest_readl(s, abs.addr); + } + break; + case Quad: + if (abs.len >= 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.len >= 2) { + qtest_writew(s, abs.addr, a.value & 0xFFFF); + } + break; + case Long: + if (abs.len >= 4) { + qtest_writel(s, abs.addr, a.value & 0xFFFFFFFF); + } + break; + case Quad: + if (abs.len >= 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 (getenv("QTEST_LOG")) { + fprintf(stderr, "[Timeout]\n"); + fflush(stderr); + } + _Exit(0); +} + +/* + * Here, we interpret random bytes from the fuzzer, as a sequence of commands. + * Our commands are variable-width, so we use a separator, CMD_SEP, to specify + * the boundaries between commands. This is just a random 32-bit value, which + * is easily identified by libfuzzer+AddressSanitizer, as long as we use + * memmem. It can also be included in the fuzzer's dictionary. More details + * here: + * https://github.com/google/fuzzing/blob/master/docs/split-inputs.md + * + * As a result, the stream of bytes is converted into a sequence of commands. + * In a simplified example where CMD_SEP 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 general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) +{ + void (*ops[]) (QTestState *s, const unsigned char* , size_t) = { + op_in, + op_out, + op_read, + op_write, + 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; + sigemptyset(&sact.sa_mask); + sact.sa_flags = 0; + sact.sa_handler = handle_timeout; + sigaction(SIGALRM, &sact, NULL); + ualarm(timeout, 0); + } + + while (cmd && Size) { + /* Get the length until the next command or end of input */ + nextcmd = memmem(cmd, Size, CMD_SEP, strlen(CMD_SEP)); + 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(CMD_SEP) - 1 : nextcmd; + Size = Size - (cmd_len + sizeof(CMD_SEP) - 1); + } + _Exit(0); + } else { + flush_events(s); + wait(NULL); + } +} + +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) || + memory_region_is_romd(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_ptr_array_remove_fast(fuzzable_memoryregions, mr); + g_ptr_array_add(fuzzable_memoryregions, mr); + } + } + return 0; +} +static int locate_fuzz_objects(Object *child, void *opaque) +{ + char *pattern = opaque; + if (g_pattern_match_simple(pattern, object_get_typename(child))) { + printf("Matched Object by Type: %s\n", 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) || + memory_region_is_romd(mr)) == false) { + g_ptr_array_remove_fast(fuzzable_memoryregions, mr); + g_ptr_array_add(fuzzable_memoryregions, mr); + } + } + } + return 0; +} + +static void general_pre_fuzz(QTestState *s) +{ + if (!getenv("QEMU_FUZZ_OBJECTS")) { + usage(); + } + if (getenv("QEMU_FUZZ_TIMEOUT")) { + timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0); + } + + fuzzable_memoryregions = g_ptr_array_new(); + wordexp_t result; + wordexp(getenv("QEMU_FUZZ_OBJECTS"), &result, 0); + for (int i = 0; i < result.we_wordc; i++) { + object_child_foreach_recursive(qdev_get_machine(), + locate_fuzz_objects, + result.we_wordv[i]); + } + + printf("This process will try to fuzz the following MemoryRegions:\n"); + for (int i = 0; i < fuzzable_memoryregions->len; i++) { + MemoryRegion *mr; + mr = g_ptr_array_index(fuzzable_memoryregions, i); + printf(" * %s (size %lx)\n", + object_get_canonical_path_component(&(mr->parent_obj)), + mr->addr); + } + counter_shm_init(); +} +static GString *general_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 64 %s ", getenv("QEMU_FUZZ_ARGS")); + return cmd_line; +} + +static void register_general_fuzz_targets(void) +{ + fuzz_add_target(&(FuzzTarget){ + .name = "general-fuzz", + .description = "Fuzz based on any qemu command-line args. ", + .get_init_cmdline = general_fuzz_cmdline, + .pre_fuzz = general_pre_fuzz, + .fuzz = general_fuzz}); +} + +fuzz_target_init(register_general_fuzz_targets);
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/Makefile.include | 1 + tests/qtest/fuzz/general_fuzz.c | 467 ++++++++++++++++++++++++++++++ 2 files changed, 468 insertions(+) create mode 100644 tests/qtest/fuzz/general_fuzz.c