Add AFL_FORK_SERVER_KILL_SIGNAL environment variable.
The AFL_FORK_SERVER_KILL_SIGNAL variable allows to configure the signal
used to kill the fork server on termination.
MODIFY
afl-cmin
afl-cmin
@@ -123,6 +123,8 @@ function usage() {
"AFL_FORKSRV_INIT_TMOUT: time the fuzzer waits for the forkserver to come up\n" \
"AFL_KEEP_TRACES: leave the temporary <out_dir>/.traces directory\n" \
"AFL_KILL_SIGNAL: Signal delivered to child processes on timeout (default: SIGKILL)\n" \
+"AFL_FORK_SERVER_KILL_SIGNAL: Signal delivered to fork server processes on termination\n"
+" (default: SIGTERM)\n"
"AFL_NO_FORKSRV: run target via execve instead of using the forkserver\n" \
"AFL_CMIN_ALLOW_ANY: write tuples for crashing inputs also\n" \
"AFL_PATH: path for the afl-showmap binary if not found anywhere in PATH\n" \

MODIFY
docs/env_variables.md
docs/env_variables.md
@@ -409,11 +409,18 @@ checks or alter some of the more exotic semantics of the tool:
the afl-fuzz -g/-G command line option to control the minimum/maximum
of fuzzing input generated.
- - `AFL_KILL_SIGNAL`: Set the signal ID to be delivered to child processes on
- timeout. Unless you implement your own targets or instrumentation, you
+ - `AFL_KILL_SIGNAL`: Set the signal ID to be delivered to child processes
+ on timeout. Unless you implement your own targets or instrumentation, you
likely don't have to set it. By default, on timeout and on exit, `SIGKILL`
(`AFL_KILL_SIGNAL=9`) will be delivered to the child.
+ - `AFL_FORK_SERVER_KILL_SIGNAL`: Set the signal ID to be delivered to the
+ fork server when AFL++ is terminated. Unless you implement your
+ fork server, you likely do not have to set it. By default, `SIGTERM`
+ (`AFL_FORK_SERVER_KILL_SIGNAL=15`) will be delivered to the fork server.
+ NOTE: Uncatchable signals, such as `SIGKILL`, cause child processes of
+ the fork server to be orphaned and leaves them in a zombie state.
+
- `AFL_MAP_SIZE` sets the size of the shared map that afl-analyze, afl-fuzz,
afl-showmap, and afl-tmin create to gather instrumentation data from the
target. This must be equal or larger than the size the target was compiled

MODIFY
include/afl-fuzz.h
include/afl-fuzz.h
@@ -393,8 +393,8 @@ typedef struct afl_env_vars {
*afl_hang_tmout, *afl_forksrv_init_tmout, *afl_preload,
*afl_max_det_extras, *afl_statsd_host, *afl_statsd_port,
*afl_crash_exitcode, *afl_statsd_tags_flavor, *afl_testcache_size,
- *afl_testcache_entries, *afl_kill_signal, *afl_target_env,
- *afl_persistent_record, *afl_exit_on_time;
+ *afl_testcache_entries, *afl_child_kill_signal, *afl_fsrv_kill_signal,
+ *afl_target_env, *afl_persistent_record, *afl_exit_on_time;
} afl_env_vars_t;
@@ -1268,4 +1268,3 @@ void queue_testcase_store_mem(afl_state_t *afl, struct queue_entry *q, u8 *mem);
#endif
#endif
-

MODIFY
include/common.h
include/common.h
@@ -67,10 +67,11 @@ u8 *find_binary(u8 *fname);
u8 *find_afl_binary(u8 *own_loc, u8 *fname);
-/* Parses the kill signal environment variable, FATALs on error.
- If the env is not set, sets the env to default_signal for the signal handlers
- and returns the default_signal. */
-int parse_afl_kill_signal_env(u8 *afl_kill_signal_env, int default_signal);
+/* Parses the (numeric) kill signal environment variable passed
+ via `numeric_signal_as_str`.
+ If NULL is passed, the `default_signal` value is returned.
+ FATALs if `numeric_signal_as_str` is not a valid integer .*/
+int parse_afl_kill_signal(u8 *numeric_signal_as_str, int default_signal);
/* Read a bitmap from file fname to memory
This is for the -B option again. */
@@ -133,4 +134,3 @@ FILE *create_ffile(u8 *fn);
s32 create_file(u8 *fn);
#endif
-

MODIFY
include/envs.h
include/envs.h
@@ -110,6 +110,7 @@ static char *afl_environment_variables[] = {
"AFL_INST_RATIO",
"AFL_KEEP_TIMEOUTS",
"AFL_KILL_SIGNAL",
+ "AFL_FORK_SERVER_KILL_SIGNAL",
"AFL_KEEP_TRACES",
"AFL_KEEP_ASSEMBLY",
"AFL_LD_HARD_FAIL",
@@ -239,4 +240,3 @@ static char *afl_environment_variables[] = {
extern char *afl_environment_variables[];
#endif
-

MODIFY
include/forkserver.h
include/forkserver.h
@@ -164,6 +164,8 @@ typedef struct afl_forkserver {
void (*add_extra_func)(void *afl_ptr, u8 *mem, u32 len);
u8 child_kill_signal;
+ u8 fsrv_kill_signal;
+
u8 persistent_mode;
#ifdef __linux__

MODIFY
src/afl-analyze.c
src/afl-analyze.c
@@ -1116,7 +1116,10 @@ int main(int argc, char **argv_orig, char **envp) {
}
fsrv.child_kill_signal =
- parse_afl_kill_signal_env(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ fsrv.fsrv_kill_signal =
+ parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
+
read_initial_file();
(void)check_binary_signatures(fsrv.target_path);

MODIFY
src/afl-common.c
src/afl-common.c
@@ -456,38 +456,24 @@ u8 *find_afl_binary(u8 *own_loc, u8 *fname) {
}
-/* Parses the kill signal environment variable, FATALs on error.
- If the env is not set, sets the env to default_signal for the signal handlers
- and returns the default_signal. */
-int parse_afl_kill_signal_env(u8 *afl_kill_signal_env, int default_signal) {
- if (afl_kill_signal_env && afl_kill_signal_env[0]) {
+int parse_afl_kill_signal(u8 *numeric_signal_as_str, int default_signal) {
+
+ if (numeric_signal_as_str && numeric_signal_as_str[0]) {
char *endptr;
u8 signal_code;
- signal_code = (u8)strtoul(afl_kill_signal_env, &endptr, 10);
+ signal_code = (u8)strtoul(numeric_signal_as_str, &endptr, 10);
/* Did we manage to parse the full string? */
- if (*endptr != '\0' || endptr == (char *)afl_kill_signal_env) {
-
- FATAL("Invalid AFL_KILL_SIGNAL: %s (expected unsigned int)",
- afl_kill_signal_env);
-
- }
-
- return signal_code;
-
+ if (*endptr != '\0' || endptr == (char *)numeric_signal_as_str) {
+ FATAL("Invalid signal name: %s", numeric_signal_as_str);
} else {
-
- char *sigstr = alloc_printf("%d", default_signal);
- if (!sigstr) { FATAL("Failed to alloc mem for signal buf"); }
-
- /* Set the env for signal handler */
- setenv("AFL_KILL_SIGNAL", sigstr, 1);
- free(sigstr);
- return default_signal;
+ return signal_code;
+ }
}
+ return default_signal;
}
static inline unsigned int helper_min3(unsigned int a, unsigned int b,
@@ -1253,4 +1239,3 @@ s32 create_file(u8 *fn) {
return fd;
}
-

MODIFY
src/afl-forkserver.c
src/afl-forkserver.c
@@ -1245,8 +1245,8 @@ void afl_fsrv_kill(afl_forkserver_t *fsrv) {
if (fsrv->child_pid > 0) { kill(fsrv->child_pid, fsrv->child_kill_signal); }
if (fsrv->fsrv_pid > 0) {
- kill(fsrv->fsrv_pid, SIGTERM);
- if (waitpid(fsrv->fsrv_pid, NULL, 0) <= 0) { WARNF("error waitpid\n"); }
+ kill(fsrv->fsrv_pid, fsrv->fsrv_kill_signal);
+ waitpid(fsrv->fsrv_pid, NULL, 0);
}

MODIFY
src/afl-fuzz-state.c
src/afl-fuzz-state.c
@@ -485,10 +485,15 @@ void read_afl_environment(afl_state_t *afl, char **envp) {
#endif
} else if (!strncmp(env, "AFL_KILL_SIGNAL",
+ afl_environment_variable_len)) {
+
+ afl->afl_env.afl_child_kill_signal =
+ (u8 *)get_afl_env(afl_environment_variables[i]);
+ } else if (!strncmp(env, "AFL_FORK_SERVER_KILL_SIGNAL",
afl_environment_variable_len)) {
- afl->afl_env.afl_kill_signal =
+ afl->afl_env.afl_fsrv_kill_signal =
(u8 *)get_afl_env(afl_environment_variables[i]);
} else if (!strncmp(env, "AFL_TARGET_ENV",
@@ -657,8 +662,7 @@ void afl_states_stop(void) {
/* NOTE: We need to make sure that the parent (the forkserver) reap the child (see below). */
if (el->fsrv.child_pid > 0) kill(el->fsrv.child_pid, el->fsrv.child_kill_signal);
if (el->fsrv.fsrv_pid > 0) {
- /* This must be SIGTERM, to allow the forkserver to reap the child before exiting. */
- kill(el->fsrv.fsrv_pid, SIGTERM);
+ kill(el->fsrv.fsrv_pid, el->fsrv.fsrv_kill_signal);
/* Make sure the forkserver does not end up as zombie. */
waitpid(el->fsrv.fsrv_pid, NULL, 0);
}

MODIFY
src/afl-fuzz.c
src/afl-fuzz.c
@@ -1359,7 +1359,9 @@ int main(int argc, char **argv_orig, char **envp) {
#endif
afl->fsrv.child_kill_signal =
- parse_afl_kill_signal_env(afl->afl_env.afl_kill_signal, SIGKILL);
+ parse_afl_kill_signal(afl->afl_env.afl_child_kill_signal, SIGKILL);
+ afl->fsrv.fsrv_kill_signal =
+ parse_afl_kill_signal(afl->afl_env.afl_fsrv_kill_signal, SIGTERM);
setup_signal_handlers();
check_asan_opts(afl);

MODIFY
src/afl-showmap.c
src/afl-showmap.c
@@ -866,6 +866,8 @@ static void usage(u8 *argv0) {
"startup (in milliseconds)\n"
"AFL_KILL_SIGNAL: Signal ID delivered to child processes on timeout, "
"etc. (default: SIGKILL)\n"
+ "AFL_FORK_SERVER_KILL_SIGNAL: Signal delivered to fork server processes on termination"
+ " (default: SIGTERM)\n"
"AFL_MAP_SIZE: the shared memory size for that target. must be >= the "
"size the target was compiled for\n"
"AFL_PRELOAD: LD_PRELOAD / DYLD_INSERT_LIBRARIES settings for target\n"
@@ -1259,7 +1261,9 @@ int main(int argc, char **argv_orig, char **envp) {
be_quiet = save_be_quiet;
fsrv->child_kill_signal =
- parse_afl_kill_signal_env(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ fsrv->fsrv_kill_signal =
+ parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
if (new_map_size) {

MODIFY
src/afl-tmin.c
src/afl-tmin.c
@@ -881,6 +881,8 @@ static void usage(u8 *argv0) {
"AFL_CRASH_EXITCODE: optional child exit code to be interpreted as crash\n"
"AFL_FORKSRV_INIT_TMOUT: time spent waiting for forkserver during startup (in milliseconds)\n"
"AFL_KILL_SIGNAL: Signal ID delivered to child processes on timeout, etc. (default: SIGKILL)\n"
+ "AFL_FORK_SERVER_KILL_SIGNAL: Signal delivered to fork server processes on termination\n"
+ " (default: SIGTERM)\n"
"AFL_MAP_SIZE: the shared memory size for that target. must be >= the size\n"
" the target was compiled for\n"
"AFL_PRELOAD: LD_PRELOAD / DYLD_INSERT_LIBRARIES settings for target\n"
@@ -1196,7 +1198,10 @@ int main(int argc, char **argv_orig, char **envp) {
}
fsrv->child_kill_signal =
- parse_afl_kill_signal_env(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ parse_afl_kill_signal(getenv("AFL_KILL_SIGNAL"), SIGKILL);
+ fsrv->fsrv_kill_signal =
+ parse_afl_kill_signal(getenv("AFL_FORK_SERVER_KILL_SIGNAL"), SIGTERM);
+
if (getenv("AFL_CRASH_EXITCODE")) {

Add AFL_FORK_SERVER_KILL_SIGNAL environment variable.

The AFL_FORK_SERVER_KILL_SIGNAL variable allows to configure the signal
used to kill the fork server on termination.