Prior to this patch we raced with a very short-lived init process. Essentially,
the init process could exit before we had time to record the cgroup namespace
causing the container to abort and report ABORTING to the caller when it
actually started just fine. Let's not do this.
(This uses syscall(SYS_getpid) in the the child to retrieve the pid just in case
we're on an older glibc version and we end up in the namespace sharing branch
of the actual lxc_clone() call.)
Additionally this fixes the shortlived tests. They were faulty so far and
should have actually failed because of the cgroup namespace recording race but
the ret variable used to return from the function was not correctly
initialized. This fixes it.
Furthermore, the shortlived tests used the c->error_num variable to determine
success or failure but this is actually not correct when the container is
started daemonized.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Starting with commit
commit c5b93afba1
Author: Li Feng <lifeng68@huawei.com>
Date: Mon Jul 10 17:19:52 2017 +0800
start: dup std{in,out,err} to pty slave
In the case the container has a console with a valid slave pty file descriptor
we duplicate std{in,out,err} to the slave file descriptor so console logging
works correctly. When the container does not have a valid slave pty file
descriptor for its console and is started daemonized we should dup to
/dev/null.
Closes#1646.
Signed-off-by: Li Feng <lifeng68@huawei.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
we made std{err,in,out} a duplicate of the slave file descriptor of the console
if it existed. This meant we also duplicated all of them when we executed
application containers in the foreground even if some std{err,in,out} file
descriptor did not refer to a {p,t}ty. This blocked use cases such as:
echo foo | lxc-execute -n -- cat
which are very valid and common with application containers but less common
with system containers where we don't have to care about this. So my suggestion
is to unconditionally duplicate std{err,in,out} to the console file descriptor
if we are either running daemonized - this ensures that daemonized application
containers with a single bash shell keep on working - or when we are not
running an application container. In other cases we only duplicate those file
descriptors that actually refer to a {p,t}ty. This logic is similar to what we
do for lxc-attach already.
Refers to #1690.
Closes#2028.
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Detaching network namespaces as an unprivileged user is currently not possible
and attaching to the user namespace will mean we are not allowed to move the
network device into an ancestor network namespace.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Moving away from internal symbols we can't do hacks like we currently do in
lxc-start and call internal functions like lxc_conf_init(). This is unsafe
anyway. Instead, we should simply error out if the user didn't give us a
configuration file to use. lxc-start refuses to start in that case already.
Relates to discussion in https://github.com/lxc/go-lxc/pull/96#discussion_r155075560 .
Closes#2023.
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This also ensures that the new more efficient clone() way of sharing namespaces
is tested.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
When I first solved this problem I went for a fork() + setns() + clone() model.
This works fine but has unnecessary overhead for a couple of reasons:
- doing a full fork() including copying file descriptor table and virtual
memory
- using pipes to retrieve the pid of the second child (the actual container
process)
This can all be avoided by being a little smart in how we employ the clone()
syscall:
- using CLONE_VM will let us get rid of using pipes since we can simply write
to the handler because we share the memory with our parent
- using CLONE_VFORK will also let us get rid of using pipes since the execution
of the parent is suspended until the child returns
- using CLONE_VM will not cause virtual memory to be copied
- using CLONE_FILES will not cause the file descriptor table to be copied
Note that the intermediate clone() is used with CLONE_VM. Some glibc versions
used to reset the pid/tid to -1 when CLONE_VM was used without CLONE_THREAD.
But since the memory between parent and child is shared on CLONE_VM this would
invalidate the getpid() cache that glibc used to maintain and so getpid() in
the child would return the parent's pid. This is all fixed in newer glibc
versions where the getpid() cache is removed and the pid/tid is not reset
anymore. However, if for whatever reason you - dear commiter - somehow need to
get the pid of the dummy intermediate process for do_share_ns() you need to
call syscall(__NR_getpid) directly. The next lxc_clone() call does not employ
CLONE_VM and will be fine.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This fixes a bug introduced by:
commit 94f0035bf6
Author: Christian Brauner <christian.brauner@ubuntu.com>
Date: Thu Dec 7 15:07:26 2017 +0100
coverity: #1425924
remove logically dead condition
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Coverity's bug analysis is correct but my fix wasn't.
This commit fixes a bunch of other bugs I just spotted as well.
This unblocks #2009.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The same message exists in lxclock.c and cgmanager.c, so print the
filename along with the message.
Before this patch:
lxc-destroy -n u1
pthread_mutex_unlock returned:1 Operation not permitted
After this patch:
xc-destroy -n u1
lxclock.c: pthread_mutex_unlock returned:1 Operation not permitted
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
