diff --git a/src/basic/alloc-util.h b/src/basic/alloc-util.h
index ebe42889ea..62b591117b 100644
--- a/src/basic/alloc-util.h
+++ b/src/basic/alloc-util.h
@@ -52,8 +52,11 @@ static inline void freep(void *p) {
 
 #define _cleanup_free_ _cleanup_(freep)
 
+/* Checks the size arguments of allocation functions for overflow in multiplication. In addition, checks if either of
+ * them is 0; that is almost certainly an error (e.g., an overflow in computing _need_), so it's better to fail (and
+ * we cannot leave this check to malloc, because the behavior of malloc(0) is impl. specific). */
 static inline bool size_multiply_overflow(size_t size, size_t need) {
-        return _unlikely_(need != 0 && size > (SIZE_MAX / need));
+        return _unlikely_(need == 0 || size == 0 || size > (SIZE_MAX / need));
 }
 
 _malloc_  _alloc_(1, 2) static inline void *malloc_multiply(size_t size, size_t need) {
diff --git a/src/boot/efi/console.h b/src/boot/efi/console.h
index 10c5ce4ebd..b9ed6c70b3 100644
--- a/src/boot/efi/console.h
+++ b/src/boot/efi/console.h
@@ -9,7 +9,7 @@
 
 #define EFI_CONTROL_PRESSED             (EFI_RIGHT_CONTROL_PRESSED|EFI_LEFT_CONTROL_PRESSED)
 #define EFI_ALT_PRESSED                 (EFI_RIGHT_ALT_PRESSED|EFI_LEFT_ALT_PRESSED)
-#define KEYPRESS(keys, scan, uni) ((((UINT64)keys) << 32) | ((scan) << 16) | (uni))
+#define KEYPRESS(keys, scan, uni) ((((UINT64)keys) << 32) | (((UINT64)scan) << 16) | (uni))
 #define KEYCHAR(k) ((k) & 0xffff)
 #define CHAR_CTRL(c) ((c) - 'a' + 1)
 
diff --git a/src/core/manager.c b/src/core/manager.c
index 6e29ddde43..af84a0a769 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -892,7 +892,7 @@ static int manager_setup_notify(Manager *m) {
                 (void) mkdir_parents_label(m->notify_socket, 0755);
                 (void) unlink(m->notify_socket);
 
-                strncpy(sa.un.sun_path, m->notify_socket, sizeof(sa.un.sun_path)-1);
+                strncpy(sa.un.sun_path, m->notify_socket, sizeof(sa.un.sun_path));
                 r = bind(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
                 if (r < 0)
                         return log_error_errno(errno, "bind(%s) failed: %m", sa.un.sun_path);
diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index e9dddbc0d7..9c92d67516 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -1846,6 +1846,9 @@ static int journal_file_append_entry_internal(
 void journal_file_post_change(JournalFile *f) {
         assert(f);
 
+        if (f->fd < 0)
+                return;
+
         /* inotify() does not receive IN_MODIFY events from file
          * accesses done via mmap(). After each access we hence
          * trigger IN_MODIFY by truncating the journal file to its
diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index 8e22538ac3..ed6da4445b 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -2157,6 +2157,7 @@ static int method_cancel_scheduled_shutdown(sd_bus_message *message, void *userd
 
         if (cancelled && m->enable_wall_messages) {
                 _cleanup_(sd_bus_creds_unrefp) sd_bus_creds *creds = NULL;
+                _cleanup_free_ char *username = NULL;
                 const char *tty = NULL;
                 uid_t uid = 0;
                 int r;
@@ -2167,8 +2168,9 @@ static int method_cancel_scheduled_shutdown(sd_bus_message *message, void *userd
                         (void) sd_bus_creds_get_tty(creds, &tty);
                 }
 
+                username = uid_to_name(uid);
                 utmp_wall("The system shutdown has been cancelled",
-                          uid_to_name(uid), tty, logind_wall_tty_filter, m);
+                          username, tty, logind_wall_tty_filter, m);
         }
 
         return sd_bus_reply_method_return(message, "b", cancelled);
diff --git a/src/login/logind-utmp.c b/src/login/logind-utmp.c
index 71ebdfcfb1..8bdd4ab6bf 100644
--- a/src/login/logind-utmp.c
+++ b/src/login/logind-utmp.c
@@ -61,7 +61,7 @@ bool logind_wall_tty_filter(const char *tty, void *userdata) {
 
 static int warn_wall(Manager *m, usec_t n) {
         char date[FORMAT_TIMESTAMP_MAX] = {};
-        _cleanup_free_ char *l = NULL;
+        _cleanup_free_ char *l = NULL, *username = NULL;
         usec_t left;
         int r;
 
@@ -83,8 +83,8 @@ static int warn_wall(Manager *m, usec_t n) {
                 return 0;
         }
 
-        utmp_wall(l, uid_to_name(m->scheduled_shutdown_uid),
-                  m->scheduled_shutdown_tty, logind_wall_tty_filter, m);
+        username = uid_to_name(m->scheduled_shutdown_uid);
+        utmp_wall(l, username, m->scheduled_shutdown_tty, logind_wall_tty_filter, m);
 
         return 1;
 }
diff --git a/src/login/pam_systemd.c b/src/login/pam_systemd.c
index 8464df122c..90ccbd7a83 100644
--- a/src/login/pam_systemd.c
+++ b/src/login/pam_systemd.c
@@ -160,7 +160,7 @@ static int get_seat_from_display(const char *display, const char **seat, uint32_
         r = socket_from_display(display, &p);
         if (r < 0)
                 return r;
-        strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
+        strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path));
 
         fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
         if (fd < 0)
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 27547051c8..134c4c3b5d 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -2826,7 +2826,7 @@ static int setup_sd_notify_child(void) {
         (void) mkdir_parents(NSPAWN_NOTIFY_SOCKET_PATH, 0755);
         (void) unlink(NSPAWN_NOTIFY_SOCKET_PATH);
 
-        strncpy(sa.un.sun_path, NSPAWN_NOTIFY_SOCKET_PATH, sizeof(sa.un.sun_path)-1);
+        strncpy(sa.un.sun_path, NSPAWN_NOTIFY_SOCKET_PATH, sizeof(sa.un.sun_path));
         r = bind(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un));
         if (r < 0) {
                 safe_close(fd);
diff --git a/src/shared/dissect-image.c b/src/shared/dissect-image.c
index b6e0534b5d..710507ed5c 100644
--- a/src/shared/dissect-image.c
+++ b/src/shared/dissect-image.c
@@ -231,7 +231,7 @@ int dissect_image(
                                 .node = TAKE_PTR(n),
                         };
 
-                        m->encrypted = streq(fstype, "crypto_LUKS");
+                        m->encrypted = streq_ptr(fstype, "crypto_LUKS");
 
                         *ret = TAKE_PTR(m);
 
diff --git a/src/shared/efivars.c b/src/shared/efivars.c
index 3931bee559..da70e68c81 100644
--- a/src/shared/efivars.c
+++ b/src/shared/efivars.c
@@ -412,9 +412,13 @@ int efi_get_boot_option(
 
         if (header->path_len > 0) {
                 uint8_t *dbuf;
-                size_t dnext;
+                size_t dnext, doff;
+
+                doff = offsetof(struct boot_option, title) + title_size;
+                dbuf = buf + doff;
+                if (header->path_len > l - doff)
+                        return -EINVAL;
 
-                dbuf = buf + offsetof(struct boot_option, title) + title_size;
                 dnext = 0;
                 while (dnext < header->path_len) {
                         struct device_path *dpath;
diff --git a/src/shared/fdset.c b/src/shared/fdset.c
index 8c852f1137..5d277328c7 100644
--- a/src/shared/fdset.c
+++ b/src/shared/fdset.c
@@ -211,13 +211,16 @@ fail:
 int fdset_close_others(FDSet *fds) {
         void *e;
         Iterator i;
-        int *a;
+        int *a = NULL;
         size_t j = 0, m;
 
         m = fdset_size(fds);
-        a = newa(int, m);
-        SET_FOREACH(e, MAKE_SET(fds), i)
-                a[j++] = PTR_TO_FD(e);
+
+        if (m > 0) {
+                a = newa(int, m);
+                SET_FOREACH(e, MAKE_SET(fds), i)
+                        a[j++] = PTR_TO_FD(e);
+        }
 
         assert(j == m);
 
diff --git a/src/shared/firewall-util.c b/src/shared/firewall-util.c
index eb4f5ff616..cba52fb419 100644
--- a/src/shared/firewall-util.c
+++ b/src/shared/firewall-util.c
@@ -50,8 +50,14 @@ static int entry_fill_basics(
         entry->ip.proto = protocol;
 
         if (in_interface) {
+                size_t l;
+
+                l = strlen(in_interface);
+                assert(l < sizeof entry->ip.iniface);
+                assert(l < sizeof entry->ip.iniface_mask);
+
                 strcpy(entry->ip.iniface, in_interface);
-                memset(entry->ip.iniface_mask, 0xFF, strlen(in_interface)+1);
+                memset(entry->ip.iniface_mask, 0xFF, l + 1);
         }
         if (source) {
                 entry->ip.src = source->in;