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  1. 26 Nov, 2016 12 commits
  3. 25 Nov, 2016 8 commits
    • Merge pull request #1319 from brauner/2016-11-25/fix_logging_race · 1145b828
      Stéphane Graber authored 
      log: fix race
    • configure: do not allow variable length arrays · d8f2dda5
      Christian Brauner authored 
      There pointless and marked as optional since C11.
Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
    • log: use N/A if getpid() != gettid() when threaded · 450b6d3d
      Christian Brauner authored 
      Sample log output:

    lxc 20161125201943.819 INFO     lxc_start - start.c:lxc_check_inherited:243 - Closed inherited fd: 54.
--> lxc N/A                INFO     lxc_monitor - monitor.c:lxc_monitor_sock_name:178 - using monitor sock name lxc/ad055575fe28ddd5//var/lib/lxc
    lxc 20161125201943.958 DEBUG    lxc_commands - commands.c:lxc_cmd_handler:893 - peer has disconnected
--> lxc N/A                DEBUG    lxc_commands - commands.c:lxc_cmd_get_state:579 - 'lxc-test-concurrent-0' is in 'RUNNING' state
    lxc 20161125201943.960 DEBUG    lxc_commands - commands.c:lxc_cmd_handler:893 - peer has disconnected
    lxc 20161125201944.009 INFO     lxc_start - start.c:lxc_check_inherited:243 - Closed inherited fd: 3.
Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
    • log: fix race · 0dcdbf8a
      Christian Brauner authored 
      localtime_r() can lead to deadlocks because it calls __tzset() and
__tzconvert() internally. The deadlock stems from an interaction between these
functions and the functions in monitor.c and commands.{c,h}. The latter
functions will write to the log independent of the container thread that is
currently running. Since the monitor fork()ed it seems to duplicate the mutex
states of the time functions mentioned above causing the deadlock.
As a short termm fix, I suggest to simply disable receiving the time when
monitor.c or command.{c,h} functions are called. This should be ok, since the
[lxc monitor] will only emit a few messages and thread-safety is currently more
important than beautiful logs. The rest of the log stays the same as it was
before.

Here is an example output from logs where I printed the pid and tid of the
process that is currently writing to the log:

            lxc 20161125170200.619 INFO     lxc_start:   18695-18695: - start.c:lxc_check_inherited:243 - Closed inherited fd: 23.
            lxc 20161125170200.640 DEBUG    lxc_start:   18677-18677: - start.c:__lxc_start:1334 - Not dropping CAP_SYS_BOOT or watching utmp.
            lxc 20161125170200.640 INFO     lxc_cgroup:  18677-18677: - cgroups/cgroup.c:cgroup_init:68 - cgroup driver cgroupfs-ng initing for lxc-test-concurrent-0

----------> lxc 20150427012246.000 INFO     lxc_monitor: 13017-18622: - monitor.c:lxc_monitor_sock_name:178 - using monitor sock name lxc/ad055575fe28ddd5//var/lib/lxc

            lxc 20161125170200.662 DEBUG    lxc_cgfsng:  18677-18677: - cgroups/cgfsng.c:filter_and_set_cpus:478 - No isolated cpus detected.
            lxc 20161125170200.662 DEBUG    lxc_cgfsng:  18677-18677: - cgroups/cgfsng.c:handle_cpuset_hierarchy:648 - "cgroup.clone_children" was already set to "1".
Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
    • configure: check whether gettid() is declared · 6a22e862
      Christian Brauner authored 
      Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
    • Merge pull request #1317 from brauner/2016-11-24/cleanup_attach · 8d3786cb
      Stéphane Graber authored 
      cleanup attach
    • Merge pull request #1318 from brauner/2016-11-25/fix_logging_race · b5e39501
      Stéphane Graber authored 
      log: use thread-safe localtime_r()
    • log: use thread-safe localtime_r() · b4c42474
      Christian Brauner authored 
      This fixes a race in liblxc logging which can lead to deadlocks. The reproducer
for this issue before this is to simply compile with --enable-tests and then
run:

    lxc-test-concurrent -j 20 -m create,start,stop,destroy -D

which should deadlock.
Signed-off-by: 's avatarChristian Brauner <christian.brauner@ubuntu.com>
  5. 24 Nov, 2016 2 commits
  7. 23 Nov, 2016 2 commits
    • attach: do not send procfd to attached process · 81f466d0
      Christian Brauner authored 
      So far, we opened a file descriptor refering to proc on the host inside the
host namespace and handed that fd to the attached process in
attach_child_main(). This was done to ensure that LSM labels were correctly
setup. However, by exploiting a potential kernel bug, ptrace could be used to
prevent the file descriptor from being closed which in turn could be used by an
unprivileged container to gain access to the host namespace. Aside from this
needing an upstream kernel fix, we should make sure that we don't pass the fd
for proc itself to the attached process. However, we cannot completely prevent
this, as the attached process needs to be able to change its apparmor profile
by writing to /proc/self/attr/exec or /proc/self/attr/current. To minimize the
attack surface, we only send the fd for /proc/self/attr/exec or
/proc/self/attr/current to the attached process. To do this we introduce a
little more IPC between the child and parent:

	 * IPC mechanism: (X is receiver)
	 *   initial process        intermediate          attached
	 *        X           <---  send pid of
	 *                          attached proc,
	 *                          then exit
	 *    send 0 ------------------------------------>    X
	 *                                              [do initialization]
	 *        X  <------------------------------------  send 1
	 *   [add to cgroup, ...]
	 *    send 2 ------------------------------------>    X
	 *						[set LXC_ATTACH_NO_NEW_PRIVS]
	 *        X  <------------------------------------  send 3
	 *   [open LSM label fd]
	 *    send 4 ------------------------------------>    X
	 *   						[set LSM label]
	 *   close socket                                 close socket
	 *                                                run program

The attached child tells the parent when it is ready to have its LSM labels set
up. The parent then opens an approriate fd for the child PID to
/proc/<pid>/attr/exec or /proc/<pid>/attr/current and sends it via SCM_RIGHTS
to the child. The child can then set its LSM laben. Both sides then close the
socket fds and the child execs the requested process.
Signed-off-by: 's avatarChristian Brauner <christian.brauner@canonical.com>
    • Merge pull request #1314 from ccope/static-mac · 8f227cdc
      Christian Brauner authored 
      Configure a static MAC address on the LXC bridge
  9. 22 Nov, 2016 16 commits