diff --git a/kernel-src/sys/syscalls/clockget.c b/kernel-src/sys/syscalls/clockget.c
index 38d3a3f9..250cfe99 100644
--- a/kernel-src/sys/syscalls/clockget.c
+++ b/kernel-src/sys/syscalls/clockget.c
@@ -12,15 +12,13 @@ syscallret_t syscall_clockget(context_t *, int clockid, timespec_t *tp) {
 	switch (clockid) {
 		case CLOCK_REALTIME: {
 			timespec_t ts = timekeeper_time();
-			usercopy_touser(tp, &ts, sizeof(timespec_t));
-			ret.errno = 0;
+			ret.errno = usercopy_touser(tp, &ts, sizeof(timespec_t));
 			break;
 		}
 		case CLOCK_MONOTONIC:
 		case CLOCK_BOOTTIME: {
 			timespec_t ts = timekeeper_timefromboot();
-			usercopy_touser(tp, &ts, sizeof(timespec_t));
-			ret.errno = 0;
+			ret.errno = usercopy_touser(tp, &ts, sizeof(timespec_t));
 			break;
 		}
 		default: {
diff --git a/kernel-src/sys/syscalls/getsockopt.c b/kernel-src/sys/syscalls/getsockopt.c
index b4e3e8c7..8f0ca35d 100644
--- a/kernel-src/sys/syscalls/getsockopt.c
+++ b/kernel-src/sys/syscalls/getsockopt.c
@@ -11,6 +11,7 @@ syscallret_t syscall_getsockopt(context_t *, int fd, int level, int optname, voi
 
 	if (!IS_USER_ADDRESS(val) || !IS_USER_ADDRESS(len)) {
 		ret.errno = EFAULT;
+		return ret;
 	}
 
 	file_t *file = fd_get(fd);
diff --git a/kernel-src/sys/syscalls/hostname.c b/kernel-src/sys/syscalls/hostname.c
index 0d12ccff..ef5dc874 100644
--- a/kernel-src/sys/syscalls/hostname.c
+++ b/kernel-src/sys/syscalls/hostname.c
@@ -59,10 +59,11 @@ syscallret_t syscall_hostname(context_t *, char *unew, size_t newsize, char *uol
 	spinlock_release(&lock);
 	interrupt_set(true);
 
+	ret.errno = 0;
+
 	if (uold)
 		ret.errno = usercopy_touser(uold, old, copysize + 1);
 
-	ret.errno = 0;
-	ret.ret = 0;
+	ret.ret = ret.errno ? -1 : 0;
 	return ret;
 }
diff --git a/kernel-src/sys/syscalls/kill.c b/kernel-src/sys/syscalls/kill.c
index 81ce32f8..307c12c6 100644
--- a/kernel-src/sys/syscalls/kill.c
+++ b/kernel-src/sys/syscalls/kill.c
@@ -9,6 +9,11 @@ syscallret_t syscall_kill(context_t *context, int pid, int signal) {
 		.ret = -1
 	};
 
+	if (signal >= NSIG) {
+		ret.errno = EINVAL;
+		return ret;
+	}
+
 	int effectivepid = -1;
 
 	if (pid > 0) // specific process
diff --git a/kernel-src/sys/syscalls/killthread.c b/kernel-src/sys/syscalls/killthread.c
index 8e6d61ec..f5db0270 100644
--- a/kernel-src/sys/syscalls/killthread.c
+++ b/kernel-src/sys/syscalls/killthread.c
@@ -9,7 +9,7 @@ syscallret_t syscall_killthread(context_t *context, int pid, int tid, int signal
 		.ret = -1
 	};
 
-	if (pid < 1 || tid < 1 || signal < 0 || signal > NSIG) {
+	if (pid < 1 || tid < 1 || signal < 0 || signal >= NSIG) {
 		ret.errno = EINVAL;
 		return ret;
 	}
diff --git a/kernel-src/sys/syscalls/sigaction.c b/kernel-src/sys/syscalls/sigaction.c
index fd51f8db..f9706925 100644
--- a/kernel-src/sys/syscalls/sigaction.c
+++ b/kernel-src/sys/syscalls/sigaction.c
@@ -7,7 +7,7 @@ syscallret_t syscall_sigaction(context_t *, int sig, sigaction_t *new, sigaction
 		.ret = -1
 	};
 
-	if (sig > NSIG || sig == SIGKILL || sig == SIGSTOP) {
+	if (sig >= NSIG || sig == SIGKILL || sig == SIGSTOP) {
 		ret.errno = EINVAL;
 		return ret;
 	}