executor: abort fuse connection

If the test process is not dying after 100ms,
abort all fuse connections in the system.
This gets rid at least of simple fuse deadlocks,
let's see how well this works in all cases.

2 files changed, 72 insertions, 6 deletions

diff --git a/executor/common.h b/executor/common.h
index 5419599da..6ba88ea3b 100644
--- a/executor/common.h
+++ b/executor/common.h
@@ -116,6 +116,17 @@ static void install_segv_handler()
 #endif
 #endif
 
+#if !GOOS_linux
+#if SYZ_EXECUTOR || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER
+static void kill_and_wait(int pid, int* status)
+{
+	kill(pid, SIGKILL);
+	while (waitpid(-1, status, 0) != pid) {
+	}
+}
+#endif
+#endif
+
 #if !GOOS_windows
 #if SYZ_EXECUTOR || SYZ_THREADED || SYZ_REPEAT && SYZ_EXECUTOR_USES_FORK_SERVER
 static void sleep_ms(uint64 ms)
@@ -573,12 +584,7 @@ static void loop()
 				continue;
 #endif
 			debug("killing\n");
-#if GOOS_linux
-			kill(-pid, SIGKILL);
-#endif
-			kill(pid, SIGKILL);
-			while (waitpid(-1, &status, WAIT_FLAGS) != pid) {
-			}
+			kill_and_wait(pid, &status);
 			break;
 		}
 #if SYZ_EXECUTOR
diff --git a/executor/common_linux.h b/executor/common_linux.h
index 3c6aadd31..610586021 100644
--- a/executor/common_linux.h
+++ b/executor/common_linux.h
@@ -1424,8 +1424,14 @@ static void setup_binfmt_misc()
 #endif
 
 #if SYZ_EXECUTOR || SYZ_SANDBOX_NONE || SYZ_SANDBOX_SETUID || SYZ_SANDBOX_NAMESPACE
+#include <errno.h>
+#include <sys/mount.h>
+
 static void setup_common()
 {
+	if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
+		debug("mount(fusectl) failed: %d\n", errno);
+	}
 #if SYZ_EXECUTOR || SYZ_ENABLE_CGROUPS
 	setup_cgroups();
 	setup_binfmt_misc();
@@ -1853,6 +1859,60 @@ static int fault_injected(int fail_fd)
 }
 #endif
 
+#if SYZ_EXECUTOR || SYZ_REPEAT
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+static void kill_and_wait(int pid, int* status)
+{
+	kill(-pid, SIGKILL);
+	kill(pid, SIGKILL);
+	int i;
+	// First, give it up to 100 ms to surrender.
+	for (i = 0; i < 100; i++) {
+		if (waitpid(-1, status, WNOHANG | __WALL) == pid)
+			return;
+		usleep(1000);
+	}
+	// Now, try to abort fuse connections as they cause deadlocks,
+	// see Documentation/filesystems/fuse.txt for details.
+	// There is no good way to figure out the right connections
+	// provided that the process could use unshare(CLONE_NEWNS),
+	// so we abort all.
+	debug("kill is not working\n");
+	DIR* dir = opendir("/sys/fs/fuse/connections");
+	if (dir) {
+		for (;;) {
+			struct dirent* ent = readdir(dir);
+			if (!ent)
+				break;
+			if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
+				continue;
+			char abort[300];
+			snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort", ent->d_name);
+			int fd = open(abort, O_WRONLY);
+			if (fd == -1) {
+				debug("failed to open %s: %d\n", abort, errno);
+				continue;
+			}
+			debug("aborting fuse conn %s\n", ent->d_name);
+			write(fd, abort, 1);
+			close(fd);
+		}
+		closedir(dir);
+	} else {
+		debug("failed to open /sys/fs/fuse/connections: %d\n", errno);
+	}
+	// Now, just wait, no other options.
+	while (waitpid(-1, status, __WALL) != pid) {
+	}
+}
+#endif
+
 #if SYZ_EXECUTOR || SYZ_REPEAT && SYZ_ENABLE_CGROUPS
 #include <fcntl.h>
 #include <sys/ioctl.h>