util: fix tty_is_vc_resolve() in a container where /sys/class/tty/console/active is misleading

TODO

@@ -20,6 +20,9 @@ Bugfixes:
 * properly handle .mount unit state tracking when two mount points are stacked one on top of another on the exact same mount point.
 
 Features:
+
+* Add pretty name for seats in logind
+
 * nspawn wants dev_setup() for /dev/fd/ and friends?
 
 * selinux: merge systemd selinux access controls (dwalsh)

src/core/condition.c

@@ -223,14 +223,8 @@ bool condition_test(Condition *c) {
         case CONDITION_PATH_IS_MOUNT_POINT:
                 return (path_is_mount_point(c->parameter, true) > 0) == !c->negate;
 
-        case CONDITION_PATH_IS_READ_WRITE: {
-                struct statvfs st;
-
-                if (statvfs(c->parameter, &st) < 0)
-                        return c->negate;
-
-                return !(st.f_flag & ST_RDONLY) == !c->negate;
-        }
+        case CONDITION_PATH_IS_READ_WRITE:
+                return (path_is_read_only_fs(c->parameter) > 0) == c->negate;
 
         case CONDITION_DIRECTORY_NOT_EMPTY: {
                 int k;

src/shared/util.c

@@ -56,6 +56,7 @@
 #include <glob.h>
 #include <grp.h>
 #include <sys/mman.h>
+#include <sys/statvfs.h>
 
 #include "macro.h"
 #include "util.h"
@@ -4319,8 +4320,10 @@ bool tty_is_vc_resolve(const char *tty) {
         if (startswith(tty, "/dev/"))
                 tty += 5;
 
-        /* Resolve where /dev/console is pointing to */
-        if (streq(tty, "console"))
+        /* Resolve where /dev/console is pointing to, if /sys is
+         * actually ours (i.e. not read-only-mounted which is a sign
+         * for container setups) */
+        if (streq(tty, "console") && path_is_read_only_fs("/sys") <= 0)
                 if (read_one_line_file("/sys/class/tty/console/active", &active) >= 0) {
                         /* If multiple log outputs are configured the
                          * last one is what /dev/console points to */
@@ -6145,3 +6148,14 @@ int setrlimit_closest(int resource, const struct rlimit *rlim) {
 
         return 0;
 }
+
+int path_is_read_only_fs(const char *path) {
+        struct statvfs st;
+
+        assert(path);
+
+        if (statvfs(path, &st) < 0)
+                return -errno;
+
+        return !!(st.f_flag & ST_RDONLY);
+}

src/shared/util.h

@@ -350,6 +350,7 @@ ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll);
 ssize_t loop_write(int fd, const void *buf, size_t nbytes, bool do_poll);
 
 int path_is_mount_point(const char *path, bool allow_symlink);
+int path_is_read_only_fs(const char *path);
 
 bool is_device_path(const char *path);