From 91dd24f207a5cb93227d4a7d364f033bfd572a31 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Mon, 10 Mar 2014 21:36:01 +0100

Subject: [PATCH] nspawn: don't try mknod() of /dev/console with the correct

 major/minor

We overmount /dev/console with an external pty anyway, hence there's no

point in using the real major/minor when we create the node to

overmount. Instead, use the one of /dev/null now.

This fixes a race against the cgroup device controller setup we are

using. In case /dev/console was create before the cgroup policy was

applied all was good, but if created in the opposite order the mknod()

would fail, since creating /dev/console is not allowed by it. Creating

/dev/null instances is however permitted, and hence use it.

(cherry picked from commit eb0f0863f5af48865fb4569e2076d5f9e2313995)

---

 src/nspawn/nspawn.c | 25 ++++++++++---------------

 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c

index 84b7276..091307b 100644

--- a/src/nspawn/nspawn.c

+++ b/src/nspawn/nspawn.c

@@ -852,23 +852,19 @@ static int setup_ptmx(const char *dest) {

 }

 static int setup_dev_console(const char *dest, const char *console) {

+        _cleanup_umask_ mode_t u;

+        const char *to;

         struct stat st;

-        _cleanup_free_ char *to = NULL;

         int r;

-        _cleanup_umask_ mode_t u;

         assert(dest);

         assert(console);

         u = umask(0000);

-        if (stat(console, &st) < 0) {

-                log_error("Failed to stat %s: %m", console);

+        if (stat("/dev/null", &st) < 0) {

+                log_error("Failed to stat /dev/null: %m");

                 return -errno;

-

-        } else if (!S_ISCHR(st.st_mode)) {

-                log_error("/dev/console is not a char device");

-                return -EIO;

         }

         r = chmod_and_chown(console, 0600, 0, 0);

@@ -877,16 +873,15 @@ static int setup_dev_console(const char *dest, const char *console) {

                 return r;

         }

-        if (asprintf(&to, "%s/dev/console", dest) < 0)

-                return log_oom();

-

         /* We need to bind mount the right tty to /dev/console since

          * ptys can only exist on pts file systems. To have something

-         * to bind mount things on we create a device node first, that

-         * has the right major/minor (note that the major minor

-         * doesn't actually matter here, since we mount it over

-         * anyway). */

+         * to bind mount things on we create a device node first, and

+         * use /dev/null for that since we the cgroups device policy

+         * allows us to create that freely, while we cannot create

+         * /dev/console. (Note that the major minor doesn't actually

+         * matter here, since we mount it over anyway). */

+        to = strappenda(dest, "/dev/console");

         if (mknod(to, (st.st_mode & ~07777) | 0600, st.st_rdev) < 0) {

                 log_error("mknod() for /dev/console failed: %m");

                 return -errno;