add fuse support

1 files changed, 66 insertions, 7 deletions

diff --git a/executor/executor.cc b/executor/executor.cc
index c0cdf72f1..7f0e82ba9 100644
--- a/executor/executor.cc
+++ b/executor/executor.cc
@@ -33,7 +33,7 @@ const int kOutPipeFd = 6;
 const int kCoverFd = 5;
 const int kMaxInput = 1 << 20;
 const int kMaxOutput = 16 << 20;
-const int kMaxArgs = 6;
+const int kMaxArgs = 9;
 const int kMaxThreads = 16;
 const int kMaxCommands = 4 << 10;
 
@@ -160,6 +160,7 @@ int main()
 			fail("fork failed");
 		if (pid == 0) {
 			setpgid(0, 0);
+			unshare(CLONE_NEWNS);
 			if (flag_drop_privs) {
 				// Pre-create one thread with root privileges for execution of special syscalls (e.g. mount).
 				if (flag_threaded)
@@ -167,9 +168,11 @@ int main()
 				// TODO: 65534 is meant to be nobody
 				if (setgroups(0, NULL))
 					fail("failed to setgroups");
-				if (setresgid(65534, 65534, 65534))
+				// glibc versions do not we want -- they force all threads to setuid.
+				// We want to preserve the thread above as root.
+				if (syscall(SYS_setresgid, 65534, 65534, 65534))
 					fail("failed to setresgid");
-				if (setresuid(65534, 65534, 65534))
+				if (syscall(SYS_setresuid, 65534, 65534, 65534))
 					fail("failed to setresuid");
 			}
 			// Don't need that SIGCANCEL/SIGSETXID glibc stuff.
@@ -336,7 +339,8 @@ thread_t* schedule_call(int n, int call_index, int call_num, uint64_t num_args,
 	// Figure out whether we need root privs for this call.
 	bool root = false;
 	switch (syscalls[call_num].sys_nr) {
-	case __NR_syz_dri_open:
+	case __NR_syz_fuse_mount:
+	case __NR_syz_fuseblk_mount:
 		root = true;
 	}
 	// Find a spare thread to execute the call.
@@ -447,16 +451,16 @@ void execute_call(thread_t* th)
 	}
 	debug(")\n");
 
-	if (kMaxArgs != 6)
-		fail("inconsistent number of arguments");
-
 	cover_reset(th);
 	switch (call->sys_nr) {
 	default: {
+		if (th->num_args > 6)
+			fail("bad number of arguments");
 		th->res = syscall(call->sys_nr, th->args[0], th->args[1], th->args[2], th->args[3], th->args[4], th->args[5]);
 		break;
 	}
 	case __NR_syz_openpts: {
+		// syz_openpts(fd fd[tty], flags flags[open_flags]) fd[tty]
 		int ptyno = 0;
 		if (ioctl(th->args[0], TIOCGPTN, &ptyno) == 0) {
 			char buf[128];
@@ -468,10 +472,65 @@ void execute_call(thread_t* th)
 		}
 	}
 	case __NR_syz_dri_open: {
+		// syz_dri_open(card_id intptr, flags flags[open_flags]) fd[dri]
 		char buf[128];
 		sprintf(buf, "/dev/dri/card%lu", th->args[0]);
 		th->res = open(buf, th->args[1], 0);
 	}
+	case __NR_syz_fuse_mount: {
+		// syz_fuse_mount(target filename, mode flags[fuse_mode], uid uid, gid gid, maxread intptr, flags flags[mount_flags]) fd[fuse]
+		uint64_t target = th->args[0];
+		uint64_t mode = th->args[1];
+		uint64_t uid = th->args[2];
+		uint64_t gid = th->args[3];
+		uint64_t maxread = th->args[4];
+		uint64_t flags = th->args[5];
+
+		int fd = open("/dev/fuse", O_RDWR);
+		if (fd != -1) {
+			char buf[256];
+			sprintf(buf, "fd=%d,user_id=%lu,group_id=%lu,rootmode=0%o", fd, uid, gid, (unsigned)mode & ~3u);
+			if (maxread != 0)
+				sprintf(buf + strlen(buf), ",max_read=%lu", maxread);
+			if (mode & 1)
+				strcat(buf, ",default_permissions");
+			if (mode & 2)
+				strcat(buf, ",allow_other");
+			syscall(SYS_mount, "", target, "fuse", flags, buf);
+			// Ignore errors, maybe fuzzer can do something useful with fd alone.
+		}
+		th->res = fd;
+	}
+	case __NR_syz_fuseblk_mount: {
+		// syz_fuseblk_mount(target filename, blkdev filename, mode flags[fuse_mode], uid uid, gid gid, maxread intptr, blksize intptr, flags flags[mount_flags]) fd[fuse]
+		uint64_t target = th->args[0];
+		uint64_t blkdev = th->args[1];
+		uint64_t mode = th->args[2];
+		uint64_t uid = th->args[3];
+		uint64_t gid = th->args[4];
+		uint64_t maxread = th->args[5];
+		uint64_t blksize = th->args[6];
+		uint64_t flags = th->args[7];
+
+		int fd = open("/dev/fuse", O_RDWR);
+		if (fd != -1) {
+			if (syscall(SYS_mknod, blkdev, S_IFBLK, makedev(7, 199)) == 0) {
+				char buf[256];
+				sprintf(buf, "fd=%d,user_id=%lu,group_id=%lu,rootmode=0%o", fd, uid, gid, (unsigned)mode & ~3u);
+				if (maxread != 0)
+					sprintf(buf + strlen(buf), ",max_read=%lu", maxread);
+				if (blksize != 0)
+					sprintf(buf + strlen(buf), ",blksize=%lu", blksize);
+				if (mode & 1)
+					strcat(buf, ",default_permissions");
+				if (mode & 2)
+					strcat(buf, ",allow_other");
+				syscall(SYS_mount, blkdev, target, "fuseblk", flags, buf);
+				// Ignore errors, maybe fuzzer can do something useful with fd alone.
+			}
+		}
+		th->res = fd;
+	}
 	}
 	int errno0 = errno;
 	th->cover_size = cover_read(th);