| Message ID | 20201015134137.205958-5-alxndr@bu.edu |
|---|---|
| State | Accepted |
| Commit | 20f5a3029386363357e6fa0c2e82b35ac4914d6a |
| Headers | show |
| Series | Add a General Virtual Device Fuzzer | expand |
On 201015 0941, Alexander Bulekov wrote: > When a virtual-device tries to access some buffer in memory over DMA, we > add call-backs into the fuzzer(next commit). The fuzzer checks verifies > that the DMA request maps to a physical RAM address and fills the memory > with fuzzer-provided data. The patterns that we use to fill this memory > are specified using add_dma_pattern and clear_dma_patterns operations. > > Signed-off-by: Alexander Bulekov <alxndr@bu.edu> > Reviewed-by: Darren Kenny <darren.kenny@oracle.com> > --- > tests/qtest/fuzz/general_fuzz.c | 230 ++++++++++++++++++++++++++++++++ > 1 file changed, 230 insertions(+) > > diff --git a/tests/qtest/fuzz/general_fuzz.c b/tests/qtest/fuzz/general_fuzz.c > index ef754843ed..0fd42a16da 100644 > --- a/tests/qtest/fuzz/general_fuzz.c > +++ b/tests/qtest/fuzz/general_fuzz.c > @@ -25,6 +25,7 @@ > #include "exec/address-spaces.h" > #include "hw/qdev-core.h" > #include "hw/pci/pci.h" > +#include "hw/boards.h" > > /* > * SEPARATOR is used to separate "operations" in the fuzz input > @@ -38,12 +39,16 @@ enum cmds { > OP_WRITE, > OP_PCI_READ, > OP_PCI_WRITE, > + OP_ADD_DMA_PATTERN, > + OP_CLEAR_DMA_PATTERNS, > OP_CLOCK_STEP, > }; > > #define DEFAULT_TIMEOUT_US 100000 > #define USEC_IN_SEC 100000000 > > +#define MAX_DMA_FILL_SIZE 0x10000 > + > #define PCI_HOST_BRIDGE_CFG 0xcf8 > #define PCI_HOST_BRIDGE_DATA 0xcfc > > @@ -56,6 +61,24 @@ static useconds_t timeout = 100000; > > static bool qtest_log_enabled; > > +/* > + * 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. > @@ -84,6 +107,169 @@ static int get_io_address_cb(ram_addr_t start, ram_addr_t size, > return 0; > } > > +/* > + * 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; > + > +void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write); > + > +/* > + * 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 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 > + * general_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, bool is_write) > +{ > + /* Are we in the general-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 is not a read (what happens for a address_space_map > + * with is_write=True? Can the device use the same pointer to do reads?) > + * - The DMA request hits past the bounds of our RAM > + */ > + if (dma_patterns->len == 0 > + || len == 0 > + || mr != MACHINE(qdev_get_machine())->ram > + || is_write > + || addr > current_machine->ram_size) { > + 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, is_write); > + } > + 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, is_write); > + } > + 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 = pattern_alloc(p, ar.size); > + hwaddr l, addr1; > + MemoryRegion *mr1; > + uint8_t *ram_ptr; > + while (len > 0) { > + l = len; > + mr1 = address_space_translate(first_cpu->as, > + addr, &addr1, &l, true, > + MEMTXATTRS_UNSPECIFIED); > + > + if (!(memory_region_is_ram(mr1) || > + memory_region_is_romd(mr1))) { > + l = memory_access_size(mr1, l, addr1); > + } else { > + /* ROM/RAM case */ > + ram_ptr = qemu_map_ram_ptr(mr1->ram_block, addr1); > + memcpy(ram_ptr, buf, l); > + break; > + } > + len -= l; > + buf += l; > + addr += l; > + > + } > + 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, ar.addr, buf, ar.size); > + } ^^ This if statement should end above the qtest_memwrite... -Alex > + g_free(buf); > + > + /* 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 > @@ -346,6 +532,35 @@ static void op_pci_write(QTestState *s, const unsigned char * data, size_t len) > } > } > > +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); > @@ -405,6 +620,8 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) > [OP_WRITE] = op_write, > [OP_PCI_READ] = op_pci_read, > [OP_PCI_WRITE] = op_pci_write, > + [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; > @@ -434,6 +651,8 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) > setitimer(ITIMER_VIRTUAL, &timer, NULL); > } > > + op_clear_dma_patterns(s, NULL, 0); > + > while (cmd && Size) { > /* Get the length until the next command or end of input */ > nextcmd = memmem(cmd, Size, SEPARATOR, strlen(SEPARATOR)); > @@ -450,6 +669,7 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) > /* 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); > } > _Exit(0); > } else { > @@ -464,6 +684,9 @@ static void usage(void) > 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); > printf("Optionally: QEMU_FUZZ_TIMEOUT= Specify a custom timeout (us). " > "0 to disable. %d by default\n", timeout); > exit(0); > @@ -534,9 +757,16 @@ static void general_pre_fuzz(QTestState *s) > if (getenv("QTEST_LOG")) { > qtest_log_enabled = 1; > } > + if (getenv("QEMU_AVOID_DOUBLE_FETCH")) { > + avoid_double_fetches = 1; > + } > if (getenv("QEMU_FUZZ_TIMEOUT")) { > timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0); > } > + qts_global = s; > + > + 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(); > -- > 2.28.0 >
diff --git a/tests/qtest/fuzz/general_fuzz.c b/tests/qtest/fuzz/general_fuzz.c index ef754843ed..0fd42a16da 100644 --- a/tests/qtest/fuzz/general_fuzz.c +++ b/tests/qtest/fuzz/general_fuzz.c @@ -25,6 +25,7 @@ #include "exec/address-spaces.h" #include "hw/qdev-core.h" #include "hw/pci/pci.h" +#include "hw/boards.h" /* * SEPARATOR is used to separate "operations" in the fuzz input @@ -38,12 +39,16 @@ enum cmds { OP_WRITE, OP_PCI_READ, OP_PCI_WRITE, + OP_ADD_DMA_PATTERN, + OP_CLEAR_DMA_PATTERNS, OP_CLOCK_STEP, }; #define DEFAULT_TIMEOUT_US 100000 #define USEC_IN_SEC 100000000 +#define MAX_DMA_FILL_SIZE 0x10000 + #define PCI_HOST_BRIDGE_CFG 0xcf8 #define PCI_HOST_BRIDGE_DATA 0xcfc @@ -56,6 +61,24 @@ static useconds_t timeout = 100000; static bool qtest_log_enabled; +/* + * 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. @@ -84,6 +107,169 @@ static int get_io_address_cb(ram_addr_t start, ram_addr_t size, return 0; } +/* + * 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; + +void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr, bool is_write); + +/* + * 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 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 + * general_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, bool is_write) +{ + /* Are we in the general-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 is not a read (what happens for a address_space_map + * with is_write=True? Can the device use the same pointer to do reads?) + * - The DMA request hits past the bounds of our RAM + */ + if (dma_patterns->len == 0 + || len == 0 + || mr != MACHINE(qdev_get_machine())->ram + || is_write + || addr > current_machine->ram_size) { + 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, is_write); + } + 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, is_write); + } + 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 = pattern_alloc(p, ar.size); + hwaddr l, addr1; + MemoryRegion *mr1; + uint8_t *ram_ptr; + while (len > 0) { + l = len; + mr1 = address_space_translate(first_cpu->as, + addr, &addr1, &l, true, + MEMTXATTRS_UNSPECIFIED); + + if (!(memory_region_is_ram(mr1) || + memory_region_is_romd(mr1))) { + l = memory_access_size(mr1, l, addr1); + } else { + /* ROM/RAM case */ + ram_ptr = qemu_map_ram_ptr(mr1->ram_block, addr1); + memcpy(ram_ptr, buf, l); + break; + } + len -= l; + buf += l; + addr += l; + + } + 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, ar.addr, buf, ar.size); + } + g_free(buf); + + /* 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 @@ -346,6 +532,35 @@ static void op_pci_write(QTestState *s, const unsigned char * data, size_t len) } } +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); @@ -405,6 +620,8 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) [OP_WRITE] = op_write, [OP_PCI_READ] = op_pci_read, [OP_PCI_WRITE] = op_pci_write, + [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; @@ -434,6 +651,8 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) setitimer(ITIMER_VIRTUAL, &timer, NULL); } + op_clear_dma_patterns(s, NULL, 0); + while (cmd && Size) { /* Get the length until the next command or end of input */ nextcmd = memmem(cmd, Size, SEPARATOR, strlen(SEPARATOR)); @@ -450,6 +669,7 @@ static void general_fuzz(QTestState *s, const unsigned char *Data, size_t Size) /* 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); } _Exit(0); } else { @@ -464,6 +684,9 @@ static void usage(void) 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); printf("Optionally: QEMU_FUZZ_TIMEOUT= Specify a custom timeout (us). " "0 to disable. %d by default\n", timeout); exit(0); @@ -534,9 +757,16 @@ static void general_pre_fuzz(QTestState *s) if (getenv("QTEST_LOG")) { qtest_log_enabled = 1; } + if (getenv("QEMU_AVOID_DOUBLE_FETCH")) { + avoid_double_fetches = 1; + } if (getenv("QEMU_FUZZ_TIMEOUT")) { timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0); } + qts_global = s; + + 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();