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authorAlban Crequy <alban@endocode.com>2015-03-31 17:14:48 +0200
committerLennart Poettering <lennart@poettering.net>2015-03-31 17:21:03 +0200
commit81f5049b7c35752182e855cdb06d707db92d7ac8 (patch)
tree8043f5c94ac2053b0f6296b1ec61329fb9409932
parent4f923a1984476de3441922ee5bf7102ebdd250ef (diff)
nspawn: fallback on bind mount when mknod fails
Some systems abusively restrict mknod, even when the device node already exists in /dev. This is unfortunate because it prevents systemd-nspawn from creating the basic devices in /dev in the container. This patch implements a workaround: when mknod fails, fallback on bind mounts. Additionally, /dev/console was created with a mknod with the same major/minor as /dev/null before bind mounting a pts on it. This patch removes the mknod and creates an empty regular file instead. In order to test this patch, I used the following configuration, which I think should replicate the system with the abusive restriction on mknod: # grep devices /proc/self/cgroup 4:devices:/user.slice/restrict # cat /sys/fs/cgroup/devices/user.slice/restrict/devices.list c 1:9 r c 5:2 rw c 136:* rw # systemd-nspawn --register=false -D . v2: - remove "bind", it is not needed since there is already MS_BIND v3: - fix error management when calling touch() - fix lowercase in error message
-rw-r--r--src/nspawn/nspawn.c29
1 files changed, 16 insertions, 13 deletions
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index b8301410cd..7e56cf2056 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -1449,8 +1449,18 @@ static int copy_devnodes(const char *dest) {
return -r;
}
- if (mknod(to, st.st_mode, st.st_rdev) < 0)
- return log_error_errno(errno, "mknod(%s) failed: %m", to);
+ if (mknod(to, st.st_mode, st.st_rdev) < 0) {
+ if (errno != EPERM)
+ return log_error_errno(errno, "mknod(%s) failed: %m", to);
+
+ /* Some systems abusively restrict mknod but
+ * allow bind mounts. */
+ r = touch(to);
+ if (r < 0)
+ return log_error_errno(r, "touch (%s) failed: %m", to);
+ if (mount(from, to, NULL, MS_BIND, NULL) < 0)
+ return log_error_errno(errno, "Both mknod and bind mount (%s) failed: %m", to);
+ }
if (arg_userns && arg_uid_shift != UID_INVALID)
if (lchown(to, arg_uid_shift, arg_uid_shift) < 0)
@@ -1481,7 +1491,6 @@ 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;
int r;
assert(dest);
@@ -1489,24 +1498,18 @@ static int setup_dev_console(const char *dest, const char *console) {
u = umask(0000);
- if (stat("/dev/null", &st) < 0)
- return log_error_errno(errno, "Failed to stat /dev/null: %m");
-
r = chmod_and_chown(console, 0600, 0, 0);
if (r < 0)
return log_error_errno(r, "Failed to correct access mode for TTY: %m");
/* 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, 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 bind mount things on we create a empty regular file. */
to = strjoina(dest, "/dev/console");
- if (mknod(to, (st.st_mode & ~07777) | 0600, st.st_rdev) < 0)
- return log_error_errno(errno, "mknod() for /dev/console failed: %m");
+ r = touch(to);
+ if (r < 0)
+ return log_error_errno(r, "touch() for /dev/console failed: %m");
if (mount(console, to, NULL, MS_BIND, NULL) < 0)
return log_error_errno(errno, "Bind mount for /dev/console failed: %m");