executor: implement support for leak checking

Leak checking support was half done and did not really work.
This is heavy-lifting to make it work.

1. Move leak/fault setup into executor.
pkg/host was a wrong place for them because we need then in C repros too.
The pkg/host periodic callback functionality did not work too,
we need it in executor so that we can reuse it in C repros too.
Remove setup/callback functions in pkg/host entirely.

2. Do leak setup/checking in C repros.
The way leak checking is invoked is slightly different from fuzzer,
but much better then no support at all.
At least the checking code is shared.

3. Add Leak option to pkg/csource and -leak flag to syz-prog2c.

4. Don't enalbe leak checking in fuzzer while we are triaging initial corpus.
It's toooo slow.

5. Fix pkg/repro to do something more sane for leak bugs.

Few other minor fixes here and there.

executor/common.h

@@ -145,7 +145,8 @@ static void sleep_ms(uint64 ms)
 }
 #endif
 
-#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER
+#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER || \
+    SYZ_ENABLE_LEAK
 #include <time.h>
 
 static uint64 current_time_ms(void)
@@ -218,7 +219,7 @@ static void remove_dir(const char* dir)
 #endif
 
 #if !GOOS_linux
-#if SYZ_EXECUTOR || SYZ_FAULT_INJECTION
+#if SYZ_EXECUTOR
 static int inject_fault(int nth)
 {
 	return 0;
@@ -637,6 +638,11 @@ static void loop(void)
 #endif
 #if SYZ_EXECUTOR || SYZ_USE_TMP_DIR
 		remove_dir(cwdbuf);
+#endif
+#if SYZ_ENABLE_LEAK
+		// Note: this will fail under setuid sandbox because we don't have
+		// write permissions for the kmemleak file.
+		check_leaks();
 #endif
 	}
 }
@@ -686,6 +692,16 @@ int main(void)
 	/*MMAP_DATA*/
 #endif
 
+#if SYZ_ENABLE_BINFMT_MISC
+	setup_binfmt_misc();
+#endif
+#if SYZ_ENABLE_LEAK
+	setup_leak();
+#endif
+#if SYZ_FAULT_INJECTION
+	setup_fault();
+#endif
+
 #if SYZ_HANDLE_SEGV
 	install_segv_handler();
 #endif
@@ -705,6 +721,9 @@ int main(void)
 		}
 	}
 	sleep(1000000);
+#endif
+#if !SYZ_PROCS && !SYZ_REPEAT && SYZ_ENABLE_LEAK
+	check_leaks();
 #endif
 	return 0;
 }

executor/common_linux.h

@@ -71,7 +71,8 @@ static int event_timedwait(event_t* ev, uint64 timeout)
 #endif
 
 #if SYZ_EXECUTOR || SYZ_REPEAT || SYZ_TUN_ENABLE || SYZ_FAULT_INJECTION || SYZ_SANDBOX_NONE || \
-    SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP
+    SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP ||        \
+    SYZ_FAULT_INJECTION || SYZ_ENABLE_LEAK || SYZ_ENABLE_BINFMT_MISC
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
@@ -1868,26 +1869,6 @@ void initialize_cgroups()
 #endif
 #endif
 
-#if SYZ_EXECUTOR || (SYZ_ENABLE_BINFMT_MISC && (SYZ_SANDBOX_NONE || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP))
-#include <fcntl.h>
-#include <sys/mount.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-
-static void setup_binfmt_misc()
-{
-#if SYZ_EXECUTOR
-	if (!flag_enable_binfmt_misc)
-		return;
-#endif
-	if (mount(0, "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, 0)) {
-		debug("mount(binfmt_misc) failed: %d\n", errno);
-	}
-	write_file("/proc/sys/fs/binfmt_misc/register", ":syz0:M:0:\x01::./file0:");
-	write_file("/proc/sys/fs/binfmt_misc/register", ":syz1:M:1:\x02::./file0:POC");
-}
-#endif
-
 #if SYZ_EXECUTOR || SYZ_SANDBOX_NONE || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP
 #include <errno.h>
 #include <sys/mount.h>
@@ -1900,9 +1881,6 @@ static void setup_common()
 #if SYZ_EXECUTOR || SYZ_ENABLE_CGROUPS
 	setup_cgroups();
 #endif
-#if SYZ_EXECUTOR || SYZ_ENABLE_BINFMT_MISC
-	setup_binfmt_misc();
-#endif
 }
 
 #include <sched.h>
@@ -2475,10 +2453,6 @@ retry:
 
 static int inject_fault(int nth)
 {
-#if SYZ_EXECUTOR
-	if (!flag_enable_fault_injection)
-		return 0;
-#endif
 	int fd;
 	fd = open("/proc/thread-self/fail-nth", O_RDWR);
 	// We treat errors here as temporal/non-critical because we see
@@ -2497,8 +2471,6 @@ static int inject_fault(int nth)
 #if SYZ_EXECUTOR
 static int fault_injected(int fail_fd)
 {
-	if (!flag_enable_fault_injection)
-		return 0;
 	char buf[16];
 	int n = read(fail_fd, buf, sizeof(buf) - 1);
 	if (n <= 0)
@@ -2646,3 +2618,153 @@ static void close_fds()
 		close(fd);
 }
 #endif
+
+#if SYZ_EXECUTOR || SYZ_FAULT_INJECTION
+#include <errno.h>
+
+static void setup_fault()
+{
+	static struct {
+		const char* file;
+		const char* val;
+		bool fatal;
+	} files[] = {
+	    {"/sys/kernel/debug/failslab/ignore-gfp-wait", "N", true},
+	    // These are enabled by separate configs (e.g. CONFIG_FAIL_FUTEX)
+	    // and we did not check all of them in host.checkFaultInjection, so we ignore errors.
+	    {"/sys/kernel/debug/fail_futex/ignore-private", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/min-order", "0", false},
+	};
+	unsigned i;
+	for (i = 0; i < sizeof(files) / sizeof(files[0]); i++) {
+		if (!write_file(files[i].file, files[i].val)) {
+			debug("failed to write %s: %d\n", files[i].file, errno);
+			if (files[i].fatal)
+				fail("failed to write %s", files[i].file);
+		}
+	}
+}
+#endif
+
+#if SYZ_EXECUTOR || SYZ_ENABLE_LEAK
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#define KMEMLEAK_FILE "/sys/kernel/debug/kmemleak"
+
+static void setup_leak()
+{
+	// Flush boot leaks.
+	if (!write_file(KMEMLEAK_FILE, "scan"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+	sleep(5); // account for MSECS_MIN_AGE
+	if (!write_file(KMEMLEAK_FILE, "scan"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+	if (!write_file(KMEMLEAK_FILE, "clear"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+}
+
+#define SYZ_HAVE_LEAK_CHECK 1
+#if SYZ_EXECUTOR
+static void check_leaks(char** frames, int nframes)
+#else
+static void check_leaks(void)
+#endif
+{
+	int fd = open(KMEMLEAK_FILE, O_RDWR);
+	if (fd == -1)
+		fail("failed to open(\"%s\")", KMEMLEAK_FILE);
+	// KMEMLEAK has false positives. To mitigate most of them, it checksums
+	// potentially leaked objects, and reports them only on the next scan
+	// iff the checksum does not change. Because of that we do the following
+	// intricate dance:
+	// Scan, sleep, scan again. At this point we can get some leaks.
+	// If there are leaks, we sleep and scan again, this can remove
+	// false leaks. Then, read kmemleak again. If we get leaks now, then
+	// hopefully these are true positives during the previous testing cycle.
+	uint64 start = current_time_ms();
+	if (write(fd, "scan", 4) != 4)
+		fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+	sleep(1);
+	// Account for MSECS_MIN_AGE
+	// (1 second less because scanning will take at least a second).
+	while (current_time_ms() - start < 4 * 1000)
+		sleep(1);
+	if (write(fd, "scan", 4) != 4)
+		fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+	static char buf[128 << 10];
+	ssize_t n = read(fd, buf, sizeof(buf) - 1);
+	if (n < 0)
+		fail("failed to read(%s)", KMEMLEAK_FILE);
+#if SYZ_EXECUTOR
+	int nleaks = 0;
+#endif
+	if (n != 0) {
+		sleep(1);
+		if (write(fd, "scan", 4) != 4)
+			fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+		if (lseek(fd, 0, SEEK_SET) < 0)
+			fail("failed to lseek(%s)", KMEMLEAK_FILE);
+		n = read(fd, buf, sizeof(buf) - 1);
+		if (n < 0)
+			fail("failed to read(%s)", KMEMLEAK_FILE);
+		buf[n] = 0;
+		char* pos = buf;
+		char* end = buf + n;
+		while (pos < end) {
+			char* next = strstr(pos + 1, "unreferenced object");
+			if (!next)
+				next = end;
+			char prev = *next;
+			*next = 0;
+#if SYZ_EXECUTOR
+			int f;
+			for (f = 0; f < nframes; f++) {
+				if (strstr(pos, frames[f]))
+					break;
+			}
+			if (f != nframes) {
+				*next = prev;
+				pos = next;
+				continue;
+			}
+#endif
+			// BUG in output should be recognized by manager.
+			fprintf(stderr, "BUG: memory leak\n%s\n", pos);
+			*next = prev;
+			pos = next;
+#if SYZ_EXECUTOR
+			nleaks++;
+#endif
+		}
+	}
+	if (write(fd, "clear", 5) != 5)
+		fail("failed to write(%s, \"clear\")", KMEMLEAK_FILE);
+	close(fd);
+#if SYZ_EXECUTOR
+	if (nleaks)
+		doexit(1);
+#endif
+}
+#endif
+
+#if SYZ_EXECUTOR || SYZ_ENABLE_BINFMT_MISC
+#include <fcntl.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+static void setup_binfmt_misc()
+{
+	if (mount(0, "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, 0)) {
+		debug("mount(binfmt_misc) failed: %d\n", errno);
+	}
+	write_file("/proc/sys/fs/binfmt_misc/register", ":syz0:M:0:\x01::./file0:");
+	write_file("/proc/sys/fs/binfmt_misc/register", ":syz1:M:1:\x02::./file0:POC");
+}
+#endif

executor/executor.cc

@@ -113,12 +113,10 @@ static bool flag_debug;
 static bool flag_cover;
 static sandbox_type flag_sandbox;
 static bool flag_extra_cover;
-static bool flag_enable_fault_injection;
 static bool flag_enable_tun;
 static bool flag_enable_net_dev;
 static bool flag_enable_net_reset;
 static bool flag_enable_cgroups;
-static bool flag_enable_binfmt_misc;
 static bool flag_enable_close_fds;
 
 static bool flag_collect_cover;
@@ -287,6 +285,11 @@ struct kcov_comparison_t {
 	bool operator<(const struct kcov_comparison_t& other) const;
 };
 
+struct feature_t {
+	const char* name;
+	void (*setup)();
+};
+
 static thread_t* schedule_call(int call_index, int call_num, bool colliding, uint64 copyout_index, uint64 num_args, uint64* args, uint64* pos);
 static void handle_completion(thread_t* th);
 static void copyout_call_results(thread_t* th);
@@ -303,6 +306,7 @@ static uint64 swap(uint64 v, uint64 size, uint64 bf);
 static void copyin(char* addr, uint64 val, uint64 size, uint64 bf, uint64 bf_off, uint64 bf_len);
 static bool copyout(char* addr, uint64 size, uint64* res);
 static void setup_control_pipes();
+static void setup_features(char** enable, int n);
 
 #include "syscalls.h"
 
@@ -330,6 +334,18 @@ int main(int argc, char** argv)
 		puts(GOOS " " GOARCH " " SYZ_REVISION " " GIT_REVISION);
 		return 0;
 	}
+	if (argc >= 2 && strcmp(argv[1], "setup") == 0) {
+		setup_features(argv + 2, argc - 2);
+		return 0;
+	}
+	if (argc >= 2 && strcmp(argv[1], "leak") == 0) {
+#if SYZ_HAVE_LEAK_CHECK
+		check_leaks(argv + 2, argc - 2);
+#else
+		fail("leak checking is not implemented");
+#endif
+		return 0;
+	}
 	if (argc == 2 && strcmp(argv[1], "test") == 0)
 		return run_tests();
 
@@ -449,13 +465,11 @@ void parse_env_flags(uint64 flags)
 	else if (flags & (1 << 4))
 		flag_sandbox = sandbox_android_untrusted_app;
 	flag_extra_cover = flags & (1 << 5);
-	flag_enable_fault_injection = flags & (1 << 6);
+	flag_enable_tun = flags & (1 << 6);
-	flag_enable_tun = flags & (1 << 7);
+	flag_enable_net_dev = flags & (1 << 7);
-	flag_enable_net_dev = flags & (1 << 8);
+	flag_enable_net_reset = flags & (1 << 8);
-	flag_enable_net_reset = flags & (1 << 9);
+	flag_enable_cgroups = flags & (1 << 9);
-	flag_enable_cgroups = flags & (1 << 10);
+	flag_enable_close_fds = flags & (1 << 10);
-	flag_enable_binfmt_misc = flags & (1 << 11);
-	flag_enable_close_fds = flags & (1 << 12);
 }
 
 #if SYZ_EXECUTOR_USES_FORK_SERVER
@@ -1359,6 +1373,26 @@ bool kcov_comparison_t::operator<(const struct kcov_comparison_t& other) const
 }
 #endif
 
+void setup_features(char** enable, int n)
+{
+	// This does any one-time setup for the requested features on the machine.
+	// Note: this can be called multiple times and must be idempotent.
+	for (int i = 0; i < n; i++) {
+		bool found = false;
+#if SYZ_HAVE_FEATURES
+		for (unsigned f = 0; f < sizeof(features) / sizeof(features[0]); f++) {
+			if (strcmp(enable[i], features[f].name) == 0) {
+				features[f].setup();
+				found = true;
+				break;
+			}
+		}
+#endif
+		if (!found)
+			fail("unknown feature %s", enable[i]);
+	}
+}
+
 void fail(const char* msg, ...)
 {
 	int e = errno;

executor/executor_linux.h

@@ -167,3 +167,10 @@ NORETURN void doexit(int status)
 	for (i = 0;; i++) {
 	}
 }
+
+#define SYZ_HAVE_FEATURES 1
+static feature_t features[] = {
+    {"leak", setup_leak},
+    {"fault", setup_fault},
+    {"binfmt_misc", setup_binfmt_misc},
+};

pkg/csource/common.go

@@ -8,6 +8,7 @@ package csource
 import (
 	"bytes"
 	"fmt"
+	"regexp"
 	"runtime"
 	"sort"
 	"strings"
@@ -61,6 +62,7 @@ func createCommonHeader(p, mmapProg *prog.Prog, replacements map[string]string,
 	} {
 		src = bytes.Replace(src, []byte(from), []byte(to), -1)
 	}
+	src = regexp.MustCompile("#define SYZ_HAVE_.*").ReplaceAll(src, nil)
 
 	return src, nil
 }
@@ -84,6 +86,7 @@ func defineList(p, mmapProg *prog.Prog, opts Options) (defines []string) {
 		"SYZ_REPEAT_TIMES":                  opts.RepeatTimes > 1,
 		"SYZ_PROCS":                         opts.Procs > 1,
 		"SYZ_FAULT_INJECTION":               opts.Fault,
+		"SYZ_ENABLE_LEAK":                   opts.Leak,
 		"SYZ_TUN_ENABLE":                    opts.EnableTun,
 		"SYZ_ENABLE_CGROUPS":                opts.EnableCgroups,
 		"SYZ_ENABLE_NETDEV":                 opts.EnableNetDev,

pkg/csource/csource.go

@@ -174,12 +174,6 @@ func (ctx *context) generateCalls(p prog.ExecProg, trace bool) ([]string, []uint
 		}
 
 		if ctx.opts.Fault && ctx.opts.FaultCall == ci {
-			// Note: these files are also hardcoded in pkg/host/host_linux.go.
-			fmt.Fprintf(w, "\twrite_file(\"/sys/kernel/debug/failslab/ignore-gfp-wait\", \"N\");\n")
-			fmt.Fprintf(w, "\twrite_file(\"/sys/kernel/debug/fail_futex/ignore-private\", \"N\");\n")
-			fmt.Fprintf(w, "\twrite_file(\"/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem\", \"N\");\n")
-			fmt.Fprintf(w, "\twrite_file(\"/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait\", \"N\");\n")
-			fmt.Fprintf(w, "\twrite_file(\"/sys/kernel/debug/fail_page_alloc/min-order\", \"0\");\n")
 			fmt.Fprintf(w, "\tinject_fault(%v);\n", ctx.opts.FaultNth)
 		}
 		// Call itself.

pkg/csource/generated.go

@@ -130,7 +130,8 @@ static void sleep_ms(uint64 ms)
 }
 #endif
 
-#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER
+#if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER || \
+    SYZ_ENABLE_LEAK
 #include <time.h>
 
 static uint64 current_time_ms(void)
@@ -203,7 +204,7 @@ static void remove_dir(const char* dir)
 #endif
 
 #if !GOOS_linux
-#if SYZ_EXECUTOR || SYZ_FAULT_INJECTION
+#if SYZ_EXECUTOR
 static int inject_fault(int nth)
 {
 	return 0;
@@ -1072,7 +1073,8 @@ static int event_timedwait(event_t* ev, uint64 timeout)
 #endif
 
 #if SYZ_EXECUTOR || SYZ_REPEAT || SYZ_TUN_ENABLE || SYZ_FAULT_INJECTION || SYZ_SANDBOX_NONE || \
-    SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP
+    SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP ||        \
+    SYZ_FAULT_INJECTION || SYZ_ENABLE_LEAK || SYZ_ENABLE_BINFMT_MISC
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
@@ -4156,26 +4158,6 @@ void initialize_cgroups()
 #endif
 #endif
 
-#if SYZ_EXECUTOR || (SYZ_ENABLE_BINFMT_MISC && (SYZ_SANDBOX_NONE || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP))
-#include <fcntl.h>
-#include <sys/mount.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-
-static void setup_binfmt_misc()
-{
-#if SYZ_EXECUTOR
-	if (!flag_enable_binfmt_misc)
-		return;
-#endif
-	if (mount(0, "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, 0)) {
-		debug("mount(binfmt_misc) failed: %d\n", errno);
-	}
-	write_file("/proc/sys/fs/binfmt_misc/register", ":syz0:M:0:\x01::./file0:");
-	write_file("/proc/sys/fs/binfmt_misc/register", ":syz1:M:1:\x02::./file0:POC");
-}
-#endif
-
 #if SYZ_EXECUTOR || SYZ_SANDBOX_NONE || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE || SYZ_SANDBOX_ANDROID_UNTRUSTED_APP
 #include <errno.h>
 #include <sys/mount.h>
@@ -4188,9 +4170,6 @@ static void setup_common()
 #if SYZ_EXECUTOR || SYZ_ENABLE_CGROUPS
 	setup_cgroups();
 #endif
-#if SYZ_EXECUTOR || SYZ_ENABLE_BINFMT_MISC
-	setup_binfmt_misc();
-#endif
 }
 
 #include <sched.h>
@@ -4687,10 +4666,6 @@ retry:
 
 static int inject_fault(int nth)
 {
-#if SYZ_EXECUTOR
-	if (!flag_enable_fault_injection)
-		return 0;
-#endif
 	int fd;
 	fd = open("/proc/thread-self/fail-nth", O_RDWR);
 	if (fd == -1)
@@ -4706,8 +4681,6 @@ static int inject_fault(int nth)
 #if SYZ_EXECUTOR
 static int fault_injected(int fail_fd)
 {
-	if (!flag_enable_fault_injection)
-		return 0;
 	char buf[16];
 	int n = read(fail_fd, buf, sizeof(buf) - 1);
 	if (n <= 0)
@@ -4842,6 +4815,142 @@ static void close_fds()
 }
 #endif
 
+#if SYZ_EXECUTOR || SYZ_FAULT_INJECTION
+#include <errno.h>
+
+static void setup_fault()
+{
+	static struct {
+		const char* file;
+		const char* val;
+		bool fatal;
+	} files[] = {
+	    {"/sys/kernel/debug/failslab/ignore-gfp-wait", "N", true},
+	    {"/sys/kernel/debug/fail_futex/ignore-private", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait", "N", false},
+	    {"/sys/kernel/debug/fail_page_alloc/min-order", "0", false},
+	};
+	unsigned i;
+	for (i = 0; i < sizeof(files) / sizeof(files[0]); i++) {
+		if (!write_file(files[i].file, files[i].val)) {
+			debug("failed to write %s: %d\n", files[i].file, errno);
+			if (files[i].fatal)
+				fail("failed to write %s", files[i].file);
+		}
+	}
+}
+#endif
+
+#if SYZ_EXECUTOR || SYZ_ENABLE_LEAK
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#define KMEMLEAK_FILE "/sys/kernel/debug/kmemleak"
+
+static void setup_leak()
+{
+	if (!write_file(KMEMLEAK_FILE, "scan"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+	sleep(5);
+	if (!write_file(KMEMLEAK_FILE, "scan"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+	if (!write_file(KMEMLEAK_FILE, "clear"))
+		fail("failed to write %s", KMEMLEAK_FILE);
+}
+
+#define SYZ_HAVE_LEAK_CHECK 1
+#if SYZ_EXECUTOR
+static void check_leaks(char** frames, int nframes)
+#else
+static void check_leaks(void)
+#endif
+{
+	int fd = open(KMEMLEAK_FILE, O_RDWR);
+	if (fd == -1)
+		fail("failed to open(\"%s\")", KMEMLEAK_FILE);
+	uint64 start = current_time_ms();
+	if (write(fd, "scan", 4) != 4)
+		fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+	sleep(1);
+	while (current_time_ms() - start < 4 * 1000)
+		sleep(1);
+	if (write(fd, "scan", 4) != 4)
+		fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+	static char buf[128 << 10];
+	ssize_t n = read(fd, buf, sizeof(buf) - 1);
+	if (n < 0)
+		fail("failed to read(%s)", KMEMLEAK_FILE);
+#if SYZ_EXECUTOR
+	int nleaks = 0;
+#endif
+	if (n != 0) {
+		sleep(1);
+		if (write(fd, "scan", 4) != 4)
+			fail("failed to write(%s, \"scan\")", KMEMLEAK_FILE);
+		if (lseek(fd, 0, SEEK_SET) < 0)
+			fail("failed to lseek(%s)", KMEMLEAK_FILE);
+		n = read(fd, buf, sizeof(buf) - 1);
+		if (n < 0)
+			fail("failed to read(%s)", KMEMLEAK_FILE);
+		buf[n] = 0;
+		char* pos = buf;
+		char* end = buf + n;
+		while (pos < end) {
+			char* next = strstr(pos + 1, "unreferenced object");
+			if (!next)
+				next = end;
+			char prev = *next;
+			*next = 0;
+#if SYZ_EXECUTOR
+			int f;
+			for (f = 0; f < nframes; f++) {
+				if (strstr(pos, frames[f]))
+					break;
+			}
+			if (f != nframes) {
+				*next = prev;
+				pos = next;
+				continue;
+			}
+#endif
+			fprintf(stderr, "BUG: memory leak\n%s\n", pos);
+			*next = prev;
+			pos = next;
+#if SYZ_EXECUTOR
+			nleaks++;
+#endif
+		}
+	}
+	if (write(fd, "clear", 5) != 5)
+		fail("failed to write(%s, \"clear\")", KMEMLEAK_FILE);
+	close(fd);
+#if SYZ_EXECUTOR
+	if (nleaks)
+		doexit(1);
+#endif
+}
+#endif
+
+#if SYZ_EXECUTOR || SYZ_ENABLE_BINFMT_MISC
+#include <fcntl.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+static void setup_binfmt_misc()
+{
+	if (mount(0, "/proc/sys/fs/binfmt_misc", "binfmt_misc", 0, 0)) {
+		debug("mount(binfmt_misc) failed: %d\n", errno);
+	}
+	write_file("/proc/sys/fs/binfmt_misc/register", ":syz0:M:0:\x01::./file0:");
+	write_file("/proc/sys/fs/binfmt_misc/register", ":syz1:M:1:\x02::./file0:POC");
+}
+#endif
+
 #elif GOOS_test
 
 #include <stdlib.h>
@@ -5261,6 +5370,9 @@ static void loop(void)
 #endif
 #if SYZ_EXECUTOR || SYZ_USE_TMP_DIR
 		remove_dir(cwdbuf);
+#endif
+#if SYZ_ENABLE_LEAK
+		check_leaks();
 #endif
 	}
 }
@@ -5308,6 +5420,16 @@ int main(void)
 	/*MMAP_DATA*/
 #endif
 
+#if SYZ_ENABLE_BINFMT_MISC
+	setup_binfmt_misc();
+#endif
+#if SYZ_ENABLE_LEAK
+	setup_leak();
+#endif
+#if SYZ_FAULT_INJECTION
+	setup_fault();
+#endif
+
 #if SYZ_HANDLE_SEGV
 	install_segv_handler();
 #endif
@@ -5327,6 +5449,9 @@ int main(void)
 		}
 	}
 	sleep(1000000);
+#endif
+#if !SYZ_PROCS && !SYZ_REPEAT && SYZ_ENABLE_LEAK
+	check_leaks();
 #endif
 	return 0;
 }

pkg/csource/options.go

@@ -28,6 +28,8 @@ type Options struct {
 	FaultCall int  `json:"fault_call,omitempty"`
 	FaultNth  int  `json:"fault_nth,omitempty"`
 
+	Leak bool `json:"leak,omitempty"` // do leak checking
+
 	// These options allow for a more fine-tuned control over the generated C code.
 	EnableTun        bool `json:"tun,omitempty"`
 	EnableNetDev     bool `json:"netdev,omitempty"`
@@ -129,6 +131,9 @@ func (opts Options) checkLinuxOnly(OS string) error {
 	if opts.Fault {
 		return fmt.Errorf("option Fault is not supported on %v", OS)
 	}
+	if opts.Leak {
+		return fmt.Errorf("option Leak is not supported on %v", OS)
+	}
 	return nil
 }
 

pkg/host/host.go

@@ -4,7 +4,11 @@
 package host
 
 import (
+	"time"
+
+	"github.com/google/syzkaller/pkg/csource"
 	"github.com/google/syzkaller/pkg/log"
+	"github.com/google/syzkaller/pkg/osutil"
 	"github.com/google/syzkaller/prog"
 )
 
@@ -67,8 +71,6 @@ type Feature struct {
 type Features [numFeatures]Feature
 
 var checkFeature [numFeatures]func() string
-var setupFeature [numFeatures]func() error
-var callbFeature [numFeatures]func(leakFrames [][]byte)
 
 func unconditionallyEnabled() string { return "" }
 
@@ -108,29 +110,20 @@ func Check(target *prog.Target) (*Features, error) {
 
 // Setup enables and does any one-time setup for the requested features on the host.
 // Note: this can be called multiple times and must be idempotent.
-func Setup(target *prog.Target, features *Features) (func(leakFrames [][]byte), error) {
+func Setup(target *prog.Target, features *Features, featureFlags csource.Features, executor string) error {
 	if target.OS == "akaros" || target.OS == "test" {
-		return nil, nil
+		return nil
 	}
-	var callback func([][]byte)
+	args := []string{"setup"}
-	for n, setup := range setupFeature {
+	if features[FeatureLeakChecking].Enabled {
-		if setup == nil || !features[n].Enabled {
+		args = append(args, "leak")
-			continue
-		}
-		if err := setup(); err != nil {
-			return nil, err
-		}
-		cb := callbFeature[n]
-		if cb == nil {
-			continue
-		}
-		prev := callback
-		callback = func(leakFrames [][]byte) {
-			cb(leakFrames)
-			if prev != nil {
-				prev(leakFrames)
-			}
-		}
 	}
-	return callback, nil
+	if features[FeatureFaultInjection].Enabled {
+		args = append(args, "fault")
+	}
+	if featureFlags["binfmt_misc"].Enabled {
+		args = append(args, "binfmt_misc")
+	}
+	_, err := osutil.RunCmd(time.Minute, "", executor, args...)
+	return err
 }

pkg/host/host_linux.go

@@ -367,10 +367,7 @@ func init() {
 	checkFeature[FeatureSandboxNamespace] = checkSandboxNamespace
 	checkFeature[FeatureSandboxAndroidUntrustedApp] = checkSandboxAndroidUntrustedApp
 	checkFeature[FeatureFaultInjection] = checkFaultInjection
-	setupFeature[FeatureFaultInjection] = setupFaultInjection
 	checkFeature[FeatureLeakChecking] = checkLeakChecking
-	setupFeature[FeatureLeakChecking] = setupLeakChecking
-	callbFeature[FeatureLeakChecking] = callbackLeakChecking
 	checkFeature[FeatureNetworkInjection] = checkNetworkInjection
 	checkFeature[FeatureNetworkDevices] = checkNetworkDevices
 }
@@ -482,28 +479,6 @@ func checkFaultInjection() string {
 	return ""
 }
 
-func setupFaultInjection() error {
-	// Note: these files are also hardcoded in pkg/csource/csource.go.
-	if err := osutil.WriteFile("/sys/kernel/debug/failslab/ignore-gfp-wait", []byte("N")); err != nil {
-		return fmt.Errorf("failed to write /failslab/ignore-gfp-wait: %v", err)
-	}
-	// These are enabled by separate configs (e.g. CONFIG_FAIL_FUTEX)
-	// and we did not check all of them in checkFaultInjection, so we ignore errors.
-	if err := osutil.WriteFile("/sys/kernel/debug/fail_futex/ignore-private", []byte("N")); err != nil {
-		log.Logf(0, "failed to write /sys/kernel/debug/fail_futex/ignore-private: %v", err)
-	}
-	if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem", []byte("N")); err != nil {
-		log.Logf(0, "failed to write /sys/kernel/debug/fail_page_alloc/ignore-gfp-highmem: %v", err)
-	}
-	if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/ignore-gfp-wait", []byte("N")); err != nil {
-		log.Logf(0, "failed to write /sys/kernel/debug/fail_page_alloc/ignore-gfp-wait: %v", err)
-	}
-	if err := osutil.WriteFile("/sys/kernel/debug/fail_page_alloc/min-order", []byte("0")); err != nil {
-		log.Logf(0, "failed to write /sys/kernel/debug/fail_page_alloc/min-order: %v", err)
-	}
-	return nil
-}
-
 func checkLeakChecking() string {
 	if reason := checkDebugFS(); reason != "" {
 		return reason
@@ -522,101 +497,6 @@ func checkLeakChecking() string {
 	return ""
 }
 
-func setupLeakChecking() error {
-	fd, err := syscall.Open("/sys/kernel/debug/kmemleak", syscall.O_RDWR, 0)
-	if err != nil {
-		return fmt.Errorf("failed to open /sys/kernel/debug/kmemleak: %v", err)
-	}
-	defer syscall.Close(fd)
-	// Flush boot leaks.
-	if _, err := syscall.Write(fd, []byte("scan")); err != nil {
-		return fmt.Errorf("write(kmemleak, scan) failed: %v", err)
-	}
-	time.Sleep(5 * time.Second) // account for MSECS_MIN_AGE
-	if _, err := syscall.Write(fd, []byte("scan")); err != nil {
-		return fmt.Errorf("write(kmemleak, scan) failed: %v", err)
-	}
-	if _, err := syscall.Write(fd, []byte("clear")); err != nil {
-		return fmt.Errorf("write(kmemleak, clear) failed: %v", err)
-	}
-	return nil
-}
-
-func callbackLeakChecking(leakFrames [][]byte) {
-	start := time.Now()
-	fd, err := syscall.Open("/sys/kernel/debug/kmemleak", syscall.O_RDWR, 0)
-	if err != nil {
-		panic(err)
-	}
-	defer syscall.Close(fd)
-	// KMEMLEAK has false positives. To mitigate most of them, it checksums
-	// potentially leaked objects, and reports them only on the next scan
-	// iff the checksum does not change. Because of that we do the following
-	// intricate dance:
-	// Scan, sleep, scan again. At this point we can get some leaks.
-	// If there are leaks, we sleep and scan again, this can remove
-	// false leaks. Then, read kmemleak again. If we get leaks now, then
-	// hopefully these are true positives during the previous testing cycle.
-	if _, err := syscall.Write(fd, []byte("scan")); err != nil {
-		panic(err)
-	}
-	time.Sleep(time.Second)
-	// Account for MSECS_MIN_AGE
-	// (1 second less because scanning will take at least a second).
-	for time.Since(start) < 4*time.Second {
-		time.Sleep(time.Second)
-	}
-	if _, err := syscall.Write(fd, []byte("scan")); err != nil {
-		panic(err)
-	}
-	buf := make([]byte, 128<<10)
-	n, err := syscall.Read(fd, buf)
-	if err != nil {
-		panic(err)
-	}
-	if n != 0 {
-		time.Sleep(time.Second)
-		if _, err := syscall.Write(fd, []byte("scan")); err != nil {
-			panic(err)
-		}
-		if _, err := syscall.Seek(fd, 0, 0); err != nil {
-			panic(err)
-		}
-		n, err := syscall.Read(fd, buf)
-		if err != nil {
-			panic(err)
-		}
-		nleaks := 0
-	nextLeak:
-		for buf = buf[:n]; len(buf) != 0; {
-			end := bytes.Index(buf[1:], []byte("unreferenced object"))
-			if end != -1 {
-				end++
-			} else {
-				end = len(buf)
-			}
-			report := buf[:end]
-			buf = buf[end:]
-			for _, frame := range leakFrames {
-				if bytes.Contains(report, frame) {
-					continue nextLeak
-				}
-			}
-			// BUG in output should be recognized by manager.
-			fmt.Printf("BUG: memory leak\n%s\n", report)
-			nleaks++
-		}
-		if nleaks != 0 {
-			// If we exit right away, dying executors will dump lots of garbage to console.
-			time.Sleep(time.Hour)
-			os.Exit(1)
-		}
-	}
-	if _, err := syscall.Write(fd, []byte("clear")); err != nil {
-		panic(err)
-	}
-}
-
 func checkSandboxNamespace() string {
 	if err := osutil.IsAccessible("/proc/self/ns/user"); err != nil {
 		return err.Error()

pkg/ipc/ipc.go

@@ -32,12 +32,10 @@ const (
 	FlagSandboxNamespace                                // use namespaces for sandboxing
 	FlagSandboxAndroidUntrustedApp                      // use Android sandboxing for the untrusted_app domain
 	FlagExtraCover                                      // collect extra coverage
-	FlagEnableFault                                     // enable fault injection support
 	FlagEnableTun                                       // setup and use /dev/tun for packet injection
 	FlagEnableNetDev                                    // setup more network devices for testing
 	FlagEnableNetReset                                  // reset network namespace between programs
 	FlagEnableCgroups                                   // setup cgroups for testing
-	FlagEnableBinfmtMisc                                // setup binfmt_misc for testing
 	FlagEnableCloseFds                                  // close fds after each program
 	// Executor does not know about these:
 	FlagUseShmem      // use shared memory instead of pipes for communication

pkg/repro/repro.go

@@ -44,8 +44,10 @@ type context struct {
 	cfg          *mgrconfig.Config
 	reporter     report.Reporter
 	crashTitle   string
+	crashType    report.Type
 	instances    chan *instance
 	bootRequests chan int
+	timeouts     []time.Duration
 	stats        *Stats
 	report       *report.Report
 }
@@ -70,22 +72,42 @@ func Run(crashLog []byte, cfg *mgrconfig.Config, reporter report.Reporter, vmPoo
 	if len(entries) == 0 {
 		return nil, nil, fmt.Errorf("crash log does not contain any programs")
 	}
-	crashStart := len(crashLog) // assuming VM hanged
+	crashStart := len(crashLog)
-	crashTitle := "hang"
+	crashTitle, crashType := "", report.Unknown
 	if rep := reporter.Parse(crashLog); rep != nil {
 		crashStart = rep.StartPos
 		crashTitle = rep.Title
+		crashType = rep.Type
+	}
+	// The shortest duration is 10 seconds to detect simple crashes (i.e. no races and no hangs).
+	// The longest duration is 6 minutes to catch races and hangs.
+	noOutputTimeout := vm.NoOutputTimeout + time.Minute
+	timeouts := []time.Duration{15 * time.Second, time.Minute, noOutputTimeout}
+	switch {
+	case crashTitle == "":
+		crashTitle = "no output/lost connection"
+		// Lost connection can be detected faster,
+		// but theoretically if it's caused by a race it may need the largest timeout.
+		// No output can only be reproduced with the max timeout.
+		// As a compromise we use the smallest and the largest timeouts.
+		timeouts = []time.Duration{15 * time.Second, noOutputTimeout}
+	case crashType == report.MemoryLeak:
+		// Memory leaks can't be detected quickly because of expensive setup and scanning.
+		timeouts = []time.Duration{time.Minute, noOutputTimeout}
+	case crashType == report.Hang:
+		timeouts = []time.Duration{noOutputTimeout}
 	}
-
 	ctx := &context{
 		cfg:          cfg,
 		reporter:     reporter,
 		crashTitle:   crashTitle,
+		crashType:    crashType,
 		instances:    make(chan *instance, len(vmIndexes)),
 		bootRequests: make(chan int, len(vmIndexes)),
+		timeouts:     timeouts,
 		stats:        new(Stats),
 	}
-	ctx.reproLog(0, "%v programs, %v VMs", len(entries), len(vmIndexes))
+	ctx.reproLog(0, "%v programs, %v VMs, timeouts %v", len(entries), len(vmIndexes), timeouts)
 	var wg sync.WaitGroup
 	wg.Add(len(vmIndexes))
 	for _, vmIndex := range vmIndexes {
@@ -252,13 +274,7 @@ func (ctx *context) extractProg(entries []*prog.LogEntry) (*Result, error) {
 	for i := len(indices) - 1; i >= 0; i-- {
 		lastEntries = append(lastEntries, entries[indices[i]])
 	}
-
+	for _, timeout := range ctx.timeouts {
-	// The shortest duration is 10 seconds to detect simple crashes (i.e. no races and no hangs).
-	// The longest duration is 6 minutes to catch races and hangs. Note that this value must be larger
-	// than hang/no output detection duration in vm.MonitorExecution, which is currently set to 5 mins.
-	timeouts := []time.Duration{10 * time.Second, 1 * time.Minute, vm.NoOutputTimeout + time.Minute}
-
-	for _, timeout := range timeouts {
 		// Execute each program separately to detect simple crashes caused by a single program.
 		// Programs are executed in reverse order, usually the last program is the guilty one.
 		res, err := ctx.extractProgSingle(reverseEntries(lastEntries), timeout)
@@ -294,6 +310,9 @@ func (ctx *context) extractProgSingle(entries []*prog.LogEntry, duration time.Du
 	ctx.reproLog(3, "single: executing %d programs separately with timeout %s", len(entries), duration)
 
 	opts := csource.DefaultOpts(ctx.cfg)
+	if ctx.crashType == report.MemoryLeak {
+		opts.Leak = true
+	}
 	for _, ent := range entries {
 		opts.Fault = ent.Fault
 		opts.FaultCall = ent.FaultCall
@@ -324,8 +343,11 @@ func (ctx *context) extractProgBisect(entries []*prog.LogEntry, baseDuration tim
 	ctx.reproLog(3, "bisect: bisecting %d programs with base timeout %s", len(entries), baseDuration)
 
 	opts := csource.DefaultOpts(ctx.cfg)
+	if ctx.crashType == report.MemoryLeak {
+		opts.Leak = true
+	}
 	duration := func(entries int) time.Duration {
-		return baseDuration + time.Duration((entries/4))*time.Second
+		return baseDuration + time.Duration(entries/4)*time.Second
 	}
 
 	// Bisect the log to find multiple guilty programs.
@@ -599,6 +621,10 @@ func (ctx *context) testImpl(inst *vm.Instance, command string, duration time.Du
 		ctx.reproLog(2, "suppressed program crash: %v", rep.Title)
 		return false, nil
 	}
+	if ctx.crashType == report.MemoryLeak && rep.Type != report.MemoryLeak {
+		ctx.reproLog(2, "not a leak crash: %v", rep.Title)
+		return false, nil
+	}
 	ctx.report = rep
 	ctx.reproLog(2, "program crashed: %v", rep.Title)
 	return true, nil

syz-fuzzer/fuzzer.go

@@ -5,6 +5,7 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"net/http"
 	_ "net/http/pprof"
 	"os"
@@ -14,6 +15,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/google/syzkaller/pkg/csource"
 	"github.com/google/syzkaller/pkg/hash"
 	"github.com/google/syzkaller/pkg/host"
 	"github.com/google/syzkaller/pkg/ipc"
@@ -27,18 +29,19 @@ import (
 )
 
 type Fuzzer struct {
-	name        string
+	name              string
-	outputType  OutputType
+	outputType        OutputType
-	config      *ipc.Config
+	config            *ipc.Config
-	execOpts    *ipc.ExecOpts
+	execOpts          *ipc.ExecOpts
-	procs       []*Proc
+	procs             []*Proc
-	gate        *ipc.Gate
+	gate              *ipc.Gate
-	workQueue   *WorkQueue
+	workQueue         *WorkQueue
-	needPoll    chan struct{}
+	needPoll          chan struct{}
-	choiceTable *prog.ChoiceTable
+	choiceTable       *prog.ChoiceTable
-	stats       [StatCount]uint64
+	stats             [StatCount]uint64
-	manager     *rpctype.RPCClient
+	manager           *rpctype.RPCClient
-	target      *prog.Target
+	target            *prog.Target
+	triagedCandidates uint32
 
 	faultInjectionEnabled    bool
 	comparisonTracingEnabled bool
@@ -180,20 +183,16 @@ func main() {
 	for _, feat := range r.CheckResult.Features {
 		log.Logf(0, "%v: %v", feat.Name, feat.Reason)
 	}
-	periodicCallback, err := host.Setup(target, r.CheckResult.Features)
+	featureFlags, err := csource.ParseFeaturesFlags("none", "none", true)
 	if err != nil {
-		log.Fatalf("BUG: %v", err)
+		log.Fatal(err)
 	}
-	var gateCallback func()
+	if err = host.Setup(target, r.CheckResult.Features, featureFlags, config.Executor); err != nil {
-	if periodicCallback != nil {
+		log.Fatal(err)
-		gateCallback = func() { periodicCallback(nil) }
 	}
 	if r.CheckResult.Features[host.FeatureExtraCoverage].Enabled {
 		config.Flags |= ipc.FlagExtraCover
 	}
-	if r.CheckResult.Features[host.FeatureFaultInjection].Enabled {
-		config.Flags |= ipc.FlagEnableFault
-	}
 	if r.CheckResult.Features[host.FeatureNetworkInjection].Enabled {
 		config.Flags |= ipc.FlagEnableTun
 	}
@@ -202,7 +201,6 @@ func main() {
 	}
 	config.Flags |= ipc.FlagEnableNetReset
 	config.Flags |= ipc.FlagEnableCgroups
-	config.Flags |= ipc.FlagEnableBinfmtMisc
 	config.Flags |= ipc.FlagEnableCloseFds
 
 	if *flagRunTest {
@@ -217,7 +215,6 @@ func main() {
 		outputType:               outputType,
 		config:                   config,
 		execOpts:                 execOpts,
-		gate:                     ipc.NewGate(2**flagProcs, gateCallback),
 		workQueue:                newWorkQueue(*flagProcs, needPoll),
 		needPoll:                 needPoll,
 		manager:                  manager,
@@ -226,6 +223,11 @@ func main() {
 		comparisonTracingEnabled: r.CheckResult.Features[host.FeatureComparisons].Enabled,
 		corpusHashes:             make(map[hash.Sig]struct{}),
 	}
+	var gateCallback func()
+	if r.CheckResult.Features[host.FeatureLeakChecking].Enabled {
+		gateCallback = func() { fuzzer.gateCallback(r.MemoryLeakFrames) }
+	}
+	fuzzer.gate = ipc.NewGate(2**flagProcs, gateCallback)
 	for i := 0; fuzzer.poll(i == 0, nil); i++ {
 	}
 	calls := make(map[*prog.Syscall]bool)
@@ -247,6 +249,30 @@ func main() {
 	fuzzer.pollLoop()
 }
 
+func (fuzzer *Fuzzer) gateCallback(leakFrames []string) {
+	// Leak checking is very slow so we don't do it while triaging the corpus
+	// (otherwise it takes infinity). When we have presumably triaged the corpus
+	// (triagedCandidates == 1), we run leak checking bug ignore the result
+	// to flush any previous leaks. After that (triagedCandidates == 2)
+	// we do actual leak checking and report leaks.
+	triagedCandidates := atomic.LoadUint32(&fuzzer.triagedCandidates)
+	if triagedCandidates == 0 {
+		return
+	}
+	args := append([]string{"leak"}, leakFrames...)
+	output, err := osutil.RunCmd(10*time.Minute, "", fuzzer.config.Executor, args...)
+	if err != nil && triagedCandidates == 2 {
+		// If we exit right away, dying executors will dump lots of garbage to console.
+		os.Stdout.Write(output)
+		fmt.Printf("BUG: leak checking failed")
+		time.Sleep(time.Hour)
+		os.Exit(1)
+	}
+	if triagedCandidates == 1 {
+		atomic.StoreUint32(&fuzzer.triagedCandidates, 2)
+	}
+}
+
 func (fuzzer *Fuzzer) pollLoop() {
 	var execTotal uint64
 	var lastPoll time.Time
@@ -321,6 +347,9 @@ func (fuzzer *Fuzzer) poll(needCandidates bool, stats map[string]uint64) bool {
 			flags: flags,
 		})
 	}
+	if needCandidates && len(r.Candidates) == 0 && atomic.LoadUint32(&fuzzer.triagedCandidates) == 0 {
+		atomic.StoreUint32(&fuzzer.triagedCandidates, 1)
+	}
 	return len(r.NewInputs) != 0 || len(r.Candidates) != 0 || maxSignal.Len() != 0
 }
 

tools/syz-execprog/execprog.go

@@ -73,16 +73,25 @@ func main() {
 			log.Logf(0, "%-24v: %v", feat.Name, feat.Reason)
 		}
 	}
-	if _, err = host.Setup(target, features); err != nil {
-		log.Fatalf("%v", err)
-	}
 	config, execOpts := createConfig(target, entries, features, featuresFlags)
-
+	if err = host.Setup(target, features, featuresFlags, config.Executor); err != nil {
+		log.Fatal(err)
+	}
+	var gateCallback func()
+	if features[host.FeatureLeakChecking].Enabled {
+		gateCallback = func() {
+			output, err := osutil.RunCmd(10*time.Minute, "", config.Executor, "leak")
+			if err != nil {
+				os.Stdout.Write(output)
+				os.Exit(1)
+			}
+		}
+	}
 	ctx := &Context{
 		entries:  entries,
 		config:   config,
 		execOpts: execOpts,
-		gate:     ipc.NewGate(2**flagProcs, nil),
+		gate:     ipc.NewGate(2**flagProcs, gateCallback),
 		shutdown: make(chan struct{}),
 		repeat:   *flagRepeat,
 	}
@@ -298,17 +307,10 @@ func createConfig(target *prog.Target, entries []*prog.LogEntry,
 		config.Flags |= ipc.FlagExtraCover
 	}
 	if *flagFaultCall >= 0 {
-		config.Flags |= ipc.FlagEnableFault
 		execOpts.Flags |= ipc.FlagInjectFault
 		execOpts.FaultCall = *flagFaultCall
 		execOpts.FaultNth = *flagFaultNth
 	}
-	for _, entry := range entries {
-		if entry.Fault {
-			config.Flags |= ipc.FlagEnableFault
-			break
-		}
-	}
 	if featuresFlags["tun"].Enabled && features[host.FeatureNetworkInjection].Enabled {
 		config.Flags |= ipc.FlagEnableTun
 	}
@@ -321,9 +323,6 @@ func createConfig(target *prog.Target, entries []*prog.LogEntry,
 	if featuresFlags["cgroups"].Enabled {
 		config.Flags |= ipc.FlagEnableCgroups
 	}
-	if featuresFlags["binfmt_misc"].Enabled {
-		config.Flags |= ipc.FlagEnableBinfmtMisc
-	}
 	if featuresFlags["close_fds"].Enabled {
 		config.Flags |= ipc.FlagEnableCloseFds
 	}

tools/syz-prog2c/prog2c.go

@@ -32,6 +32,7 @@ var (
 	flagUseTmpDir  = flag.Bool("tmpdir", false, "create a temporary dir and execute inside it")
 	flagTrace      = flag.Bool("trace", false, "trace syscall results")
 	flagStrict     = flag.Bool("strict", false, "parse input program in strict mode")
+	flagLeak       = flag.Bool("leak", false, "do leak checking")
 	flagEnable     = flag.String("enable", "none", "enable only listed additional features")
 	flagDisable    = flag.String("disable", "none", "enable all additional features except listed")
 )
@@ -79,6 +80,7 @@ func main() {
 		Fault:            *flagFaultCall >= 0,
 		FaultCall:        *flagFaultCall,
 		FaultNth:         *flagFaultNth,
+		Leak:             *flagLeak,
 		EnableTun:        features["tun"].Enabled,
 		EnableNetDev:     features["net_dev"].Enabled,
 		EnableNetReset:   features["net_reset"].Enabled,

tools/syz-stress/stress.go

@@ -67,9 +67,6 @@ func main() {
 	if err != nil {
 		log.Fatalf("%v", err)
 	}
-	if _, err = host.Setup(target, features); err != nil {
-		log.Fatalf("%v", err)
-	}
 
 	calls := buildCallList(target, strings.Split(*flagSyscalls, ","))
 	prios := target.CalculatePriorities(corpus)
@@ -91,12 +88,12 @@ func main() {
 	if featuresFlags["cgroups"].Enabled {
 		config.Flags |= ipc.FlagEnableCgroups
 	}
-	if featuresFlags["binfmt_misc"].Enabled {
-		config.Flags |= ipc.FlagEnableBinfmtMisc
-	}
 	if featuresFlags["close_fds"].Enabled {
 		config.Flags |= ipc.FlagEnableCloseFds
 	}
+	if err = host.Setup(target, features, featuresFlags, config.Executor); err != nil {
+		log.Fatal(err)
+	}
 	gate = ipc.NewGate(2**flagProcs, nil)
 	for pid := 0; pid < *flagProcs; pid++ {
 		pid := pid