1 /*
2 * fuzzing driver
3 *
4 * Copyright Red Hat Inc., 2019
5 *
6 * Authors:
7 * Alexander Bulekov <alxndr@bu.edu>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2 or later.
10 * See the COPYING file in the top-level directory.
11 *
12 */
13
14 #include "qemu/osdep.h"
15
16 #include <wordexp.h>
17
18 #include "qemu/cutils.h"
19 #include "qemu/datadir.h"
20 #include "sysemu/sysemu.h"
21 #include "sysemu/qtest.h"
22 #include "sysemu/runstate.h"
23 #include "qemu/main-loop.h"
24 #include "qemu/rcu.h"
25 #include "tests/qtest/libqtest.h"
26 #include "tests/qtest/libqos/qgraph.h"
27 #include "fuzz.h"
28
29 #define MAX_EVENT_LOOPS 10
30
31 typedef struct FuzzTargetState {
32 FuzzTarget *target;
33 QSLIST_ENTRY(FuzzTargetState) target_list;
34 } FuzzTargetState;
35
36 typedef QSLIST_HEAD(, FuzzTargetState) FuzzTargetList;
37
38 static const char *fuzz_arch = TARGET_NAME;
39
40 static FuzzTargetList *fuzz_target_list;
41 static FuzzTarget *fuzz_target;
42 static QTestState *fuzz_qts;
43
44
45
flush_events(QTestState * s)46 void flush_events(QTestState *s)
47 {
48 int i = MAX_EVENT_LOOPS;
49 while (g_main_context_pending(NULL) && i-- > 0) {
50 main_loop_wait(false);
51 }
52 }
53
fuzz_reset(QTestState * s)54 void fuzz_reset(QTestState *s)
55 {
56 qemu_system_reset(SHUTDOWN_CAUSE_GUEST_RESET);
57 main_loop_wait(true);
58 }
59
qtest_setup(void)60 static QTestState *qtest_setup(void)
61 {
62 qtest_server_set_send_handler(&qtest_client_inproc_recv, &fuzz_qts);
63 return qtest_inproc_init(&fuzz_qts, false, fuzz_arch,
64 &qtest_server_inproc_recv);
65 }
66
fuzz_add_target(const FuzzTarget * target)67 void fuzz_add_target(const FuzzTarget *target)
68 {
69 FuzzTargetState *tmp;
70 FuzzTargetState *target_state;
71 if (!fuzz_target_list) {
72 fuzz_target_list = g_new0(FuzzTargetList, 1);
73 }
74
75 QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
76 if (g_strcmp0(tmp->target->name, target->name) == 0) {
77 fprintf(stderr, "Error: Fuzz target name %s already in use\n",
78 target->name);
79 abort();
80 }
81 }
82 target_state = g_new0(FuzzTargetState, 1);
83 target_state->target = g_new0(FuzzTarget, 1);
84 *(target_state->target) = *target;
85 QSLIST_INSERT_HEAD(fuzz_target_list, target_state, target_list);
86 }
87
88
89
usage(char * path)90 static void usage(char *path)
91 {
92 printf("Usage: %s --fuzz-target=FUZZ_TARGET [LIBFUZZER ARGUMENTS]\n", path);
93 printf("where FUZZ_TARGET is one of:\n");
94 FuzzTargetState *tmp;
95 if (!fuzz_target_list) {
96 fprintf(stderr, "Fuzz target list not initialized\n");
97 abort();
98 }
99 QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
100 printf(" * %s : %s\n", tmp->target->name,
101 tmp->target->description);
102 }
103 printf("Alternatively, add -target-FUZZ_TARGET to the executable name\n\n"
104 "Set the environment variable FUZZ_SERIALIZE_QTEST=1 to serialize\n"
105 "QTest commands into an ASCII protocol. Useful for building crash\n"
106 "reproducers, but slows down execution.\n\n"
107 "Set the environment variable QTEST_LOG=1 to log all qtest commands"
108 "\n");
109 exit(0);
110 }
111
fuzz_get_target(char * name)112 static FuzzTarget *fuzz_get_target(char* name)
113 {
114 FuzzTargetState *tmp;
115 if (!fuzz_target_list) {
116 fprintf(stderr, "Fuzz target list not initialized\n");
117 abort();
118 }
119
120 QSLIST_FOREACH(tmp, fuzz_target_list, target_list) {
121 if (strcmp(tmp->target->name, name) == 0) {
122 return tmp->target;
123 }
124 }
125 return NULL;
126 }
127
128
129 /* Sometimes called by libfuzzer to mutate two inputs into one */
LLVMFuzzerCustomCrossOver(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)130 size_t LLVMFuzzerCustomCrossOver(const uint8_t *data1, size_t size1,
131 const uint8_t *data2, size_t size2,
132 uint8_t *out, size_t max_out_size,
133 unsigned int seed)
134 {
135 if (fuzz_target->crossover) {
136 return fuzz_target->crossover(data1, size1, data2, size2, out,
137 max_out_size, seed);
138 }
139 return 0;
140 }
141
142 /* Executed for each fuzzing-input */
LLVMFuzzerTestOneInput(const unsigned char * Data,size_t Size)143 int LLVMFuzzerTestOneInput(const unsigned char *Data, size_t Size)
144 {
145 /*
146 * Do the pre-fuzz-initialization before the first fuzzing iteration,
147 * instead of before the actual fuzz loop. This is needed since libfuzzer
148 * may fork off additional workers, prior to the fuzzing loop, and if
149 * pre_fuzz() sets up e.g. shared memory, this should be done for the
150 * individual worker processes
151 */
152 static int pre_fuzz_done;
153 if (!pre_fuzz_done && fuzz_target->pre_fuzz) {
154 fuzz_target->pre_fuzz(fuzz_qts);
155 pre_fuzz_done = true;
156 }
157
158 fuzz_target->fuzz(fuzz_qts, Data, Size);
159 return 0;
160 }
161
162 /* Executed once, prior to fuzzing */
LLVMFuzzerInitialize(int * argc,char *** argv,char *** envp)163 int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp)
164 {
165
166 char *target_name;
167 GString *cmd_line;
168 gchar *pretty_cmd_line;
169 bool serialize = false;
170
171 /* Initialize qgraph and modules */
172 qos_graph_init();
173 module_call_init(MODULE_INIT_FUZZ_TARGET);
174 module_call_init(MODULE_INIT_QOM);
175 module_call_init(MODULE_INIT_LIBQOS);
176
177 qemu_init_exec_dir(**argv);
178 target_name = strstr(**argv, "-target-");
179 if (target_name) { /* The binary name specifies the target */
180 target_name += strlen("-target-");
181 } else if (*argc > 1) { /* The target is specified as an argument */
182 target_name = (*argv)[1];
183 if (!strstr(target_name, "--fuzz-target=")) {
184 usage(**argv);
185 }
186 target_name += strlen("--fuzz-target=");
187 } else {
188 usage(**argv);
189 }
190
191 /* Should we always serialize qtest commands? */
192 if (getenv("FUZZ_SERIALIZE_QTEST")) {
193 serialize = true;
194 }
195
196 fuzz_qtest_set_serialize(serialize);
197
198 /* Identify the fuzz target */
199 fuzz_target = fuzz_get_target(target_name);
200 if (!fuzz_target) {
201 usage(**argv);
202 }
203
204 fuzz_qts = qtest_setup();
205
206 if (fuzz_target->pre_vm_init) {
207 fuzz_target->pre_vm_init();
208 }
209
210 /* Run QEMU's system main with the fuzz-target dependent arguments */
211 cmd_line = fuzz_target->get_init_cmdline(fuzz_target);
212 g_string_append_printf(cmd_line, " %s -qtest /dev/null ",
213 getenv("QTEST_LOG") ? "" : "-qtest-log none");
214
215 /* Split the runcmd into an argv and argc */
216 wordexp_t result;
217 wordexp(cmd_line->str, &result, 0);
218 g_string_free(cmd_line, true);
219
220 if (getenv("QTEST_LOG")) {
221 pretty_cmd_line = g_strjoinv(" ", result.we_wordv + 1);
222 printf("Starting %s with Arguments: %s\n",
223 result.we_wordv[0], pretty_cmd_line);
224 g_free(pretty_cmd_line);
225 }
226
227 qemu_init(result.we_wordc, result.we_wordv);
228
229 /* re-enable the rcu atfork, which was previously disabled in qemu_init */
230 rcu_enable_atfork();
231
232 /*
233 * Disable QEMU's signal handlers, since we manually control the main_loop,
234 * and don't check for main_loop_should_exit
235 */
236 signal(SIGINT, SIG_DFL);
237 signal(SIGHUP, SIG_DFL);
238 signal(SIGTERM, SIG_DFL);
239
240 return 0;
241 }
242