From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 14 Feb 2018 13:56:17 +0000 (+0100)
Subject: terminal-util: modernize get_kernel_consoles() a bit
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=17cf319e946a8db177ec5a150b829469a71d785a;p=elogind.git

terminal-util: modernize get_kernel_consoles() a bit

Also, make sure when we run in a container, we don't use the data from
/sys at all, but immediately fall back to /dev/console itself.
---

diff --git a/src/basic/terminal-util.c b/src/basic/terminal-util.c
index 39d3e2ce3..3c2c145b6 100644
--- a/src/basic/terminal-util.c
+++ b/src/basic/terminal-util.c
@@ -715,24 +715,29 @@ char *resolve_dev_console(char **active) {
         return tty;
 }
 
-int get_kernel_consoles(char ***consoles) {
-        _cleanup_strv_free_ char **con = NULL;
+int get_kernel_consoles(char ***ret) {
+        _cleanup_strv_free_ char **l = NULL;
         _cleanup_free_ char *line = NULL;
-        const char *active;
+        const char *p;
         int r;
 
-        assert(consoles);
+        assert(ret);
+
+        /* If we /sys is mounted read-only this means we are running in some kind of container environment. In that
+         * case /sys would reflect the host system, not us, hence ignore the data we can read from it. */
+        if (path_is_read_only_fs("/sys") > 0)
+                goto fallback;
 
         r = read_one_line_file("/sys/class/tty/console/active", &line);
         if (r < 0)
                 return r;
 
-        active = line;
+        p = line;
         for (;;) {
                 _cleanup_free_ char *tty = NULL;
                 char *path;
 
-                r = extract_first_word(&active, &tty, NULL, 0);
+                r = extract_first_word(&p, &tty, NULL, 0);
                 if (r < 0)
                         return r;
                 if (r == 0)
@@ -755,21 +760,29 @@ int get_kernel_consoles(char ***consoles) {
                         continue;
                 }
 
-                r = strv_consume(&con, path);
+                r = strv_consume(&l, path);
                 if (r < 0)
                         return r;
         }
 
-        if (strv_isempty(con)) {
+        if (strv_isempty(l)) {
                 log_debug("No devices found for system console");
-
-                r = strv_extend(&con, "/dev/console");
-                if (r < 0)
-                        return r;
+                goto fallback;
         }
 
-        *consoles = con;
-        con = NULL;
+        *ret = l;
+        l = NULL;
+
+        return 0;
+
+fallback:
+        r = strv_extend(&l, "/dev/console");
+        if (r < 0)
+                return r;
+
+        *ret = l;
+        l = NULL;
+
         return 0;
 }
 
diff --git a/src/basic/terminal-util.h b/src/basic/terminal-util.h
index 4f39bc034..b115ad95e 100644
--- a/src/basic/terminal-util.h
+++ b/src/basic/terminal-util.h
@@ -89,7 +89,7 @@ int vt_disallocate(const char *name);
 
 char *resolve_dev_console(char **active);
 #endif // 0
-int get_kernel_consoles(char ***consoles);
+int get_kernel_consoles(char ***ret);
 bool tty_is_vc(const char *tty);
 #if 0 /// UNNEEDED by elogind
 bool tty_is_vc_resolve(const char *tty);