shaba/systemd
1
0
Fork 0
mirror of https://github.com/systemd/systemd.git synced 2024-12-22 17:35:35 +03:00
Code

nspawn: fallback on bind mount when mknod fails

Browse Source 
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
This commit is contained in:
Alban Crequy 2015-03-31 17:14:48 +02:00 committed by Lennart Poettering
parent 4f923a1984
commit 81f5049b7c
1 changed files with 16 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/nspawn/nspawn.c
View File

@ -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");