BugLink: https://bugs.launchpad.net/bugs/1831258 Cc: Dimitri John Ledkov <xnox@ubuntu.com> Cc: Scott Moser <smoser@ubuntu.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
In addition to isolated cpus we also need to account for offline cpus when our
ancestor cgroup is the root cgroup and we have not been initialized yet.
Closes #2953.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Tycho Andersen [Thu, 9 May 2019 18:18:10 +0000 (14:18 -0400)]
lxc_clone: get rid of some indirection
We have a do_clone(), which just calls a void f(void *) that it gets
passed. We build up a struct consisting of two args that are just the
actual arg and actual function. Let's just have the syscall do this for us.
Tycho Andersen [Thu, 9 May 2019 17:52:30 +0000 (13:52 -0400)]
lxc_clone: pass non-stack allocated stack to clone
There are two problems with this code:
1. The math is wrong. We allocate a char *foo[__LXC_STACK_SIZE]; which
means it's really sizeof(char *) * __LXC_STACK_SIZE, instead of just
__LXC_STACK SIZE.
2. We can't actually allocate it on our stack. When we use CLONE_VM (which
we do in the shared ns case) that means that the new thread is just
running one page lower on the stack, but anything that allocates a page
on the stack may clobber data. This is a pretty short race window since
we just do the shared ns stuff and then do a clone without CLONE_VM.
However, it does point out an interesting possible privilege escalation if
things aren't configured correctly: do_share_ns() sets up namespaces while
it shares the address space of the task that spawned it; once it enters the
pid ns of the thing it's sharing with, the thing it's sharing with can
ptrace it and write stuff into the host's address space. Since the function
that does the clone() is lxc_spawn(), it has a struct cgroup_ops* on the
stack, which itself has function pointers called later in the function, so
it's possible to allocate shellcode in the address space of the host and
run it fairly easily.
ASLR doesn't mitigate this since we know exactly the stack offsets; however
this patch has the kernel allocate a new stack, which will help. Of course,
the attacker could just check /proc/pid/maps to find the location of the
stack, but they'd still have to guess where to write stuff in.
The thing that does prevent this is the default configuration of apparmor.
Since the apparmor profile is set in the second clone, and apparmor
prevents ptracing things under a different profile, attackers confined by
apparmor can't do this. However, if users are using a custom configuration
with shared namespaces, care must be taken to avoid this race.
Shared namespaces aren't widely used now, so perhaps this isn't a problem,
but with the advent of crio-lxc for k8s, this functionality will be used
more.
Thomas Parrott [Wed, 15 May 2019 14:54:12 +0000 (15:54 +0100)]
network: move phys netdevs back to monitor's net ns rather than pid 1's
Updates lxc_restore_phys_nics_to_netns() to move phys netdevs back to the monitor's network namespace rather than the previously hardcoded PID 1 net ns.
This is to fix instances where LXC is started inside a net ns different from PID 1 and physical devices are moved back to a different net ns when the container is shutdown than the net ns than where the container was started from.
Signed-off-by: Thomas Parrott <thomas.parrott@canonical.com>
Rachid Koucha [Mon, 13 May 2019 11:13:18 +0000 (13:13 +0200)]
Config: check for %m availability
GLIBC supports %m to avoid calling strerror(). Using it saves some code space.
==> This check will define HAVE_M_FORMAT to be use wherever possible (e.g. log.h)
Rachid Koucha [Fri, 10 May 2019 16:56:12 +0000 (18:56 +0200)]
lxccontainer: do not display if missing privileges
lxc-ls without root privileges on privileged containers should not display
information. In lxc_container_new(), ongoing_create()'s result is not checked
for all possible returned values. Hence, an unprivileged user can send command
messages to the container's monitor. For example:
$ lxc-ls -P /.../tests -f
NAME STATE AUTOSTART GROUPS IPV4 IPV6 UNPRIVILEGED
ctr - 0 - - - false
$ sudo lxc-ls -P /.../tests -f
NAME STATE AUTOSTART GROUPS IPV4 IPV6 UNPRIVILEGED
ctr RUNNING 0 - 10.0.3.51 - false
After this change:
$ lxc-ls -P /.../tests -f <-------- No more display without root privileges
$ sudo lxc-ls -P /.../tests -f
NAME STATE AUTOSTART GROUPS IPV4 IPV6 UNPRIVILEGED
ctr RUNNING 0 - 10.0.3.37 - false
$
Signed-off-by: Rachid Koucha <rachid.koucha@gmail.com> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Rachid Koucha [Fri, 10 May 2019 15:01:13 +0000 (17:01 +0200)]
New --bbpath option and unecessary --rootfs checks
. Add the "--bbpath" option to pass an alternate busybox pathname instead of the one found from ${PATH}.
. Take this opportunity to add some formatting in the usage display
. As a try is done to pick rootfs from the config file and set it to ${path}/rootfs, it is unnecessary to make it mandatory
Note the clone() syscall ignores unknown flags which is usually a design
mistake. However, for us this bug is a feature since we can just pass the flag
along and see whether the kernel has given us a pidfd.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Thomas Parrott [Thu, 9 May 2019 15:40:08 +0000 (16:40 +0100)]
network: Restores phys device MTU on container shutdown
The phys devices will now have their original MTUs recorded at start and restored at shutdown.
This is to protect the original phys device from having any container level MTU customisation being applied to the device once it is restored to the host.
Signed-off-by: Thomas Parrott <thomas.parrott@canonical.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Co-developed-by: David Howells <dhowells@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com>
The returns_twice attribute tells the compiler that a function may return more
than one time. The compiler will ensure that all registers are dead before
calling such a function and will emit a warning about the variables that may be
clobbered after the second return from the function. Examples of such functions
are setjmp and vfork. The longjmp-like counterpart of such function, if any,
might need to be marked with the noreturn attribute.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Felix Abecassis [Tue, 16 Apr 2019 21:40:03 +0000 (14:40 -0700)]
conf: do lxc.mount.entry mounts right after lxc.mount.fstab
These configuration options use the same syntax and therefore it seems
more intuitive to have the same behavior for both of them, which is
not the case today since mount hooks and autodev mounts are called
between the two.
See: https://github.com/lxc/lxc/issues/2932
Signed-off-by: Felix Abecassis <fabecassis@nvidia.com>
Change zfs arguments. This also works with older zfs versions, tested with
zfs 0.7.9-3 on Ubuntu 18.10.
Closes #2916.
Signed-off-by: Paul Gauret <pgauret@yahoo.com>
[christian.brauner@ubuntu.com: adapt commit message and add Signed-off-by for Paul] Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
The child_path variable is initialized very late in the function so jumping to
the on_error label would cause a nullderef. With the cleanup macros we can
simplify this function to simply do direct returns and avoid that whole issue.
Closes #2935.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
This hardens multi-threaded C. Without it, the implementation of thread
cancellation handlers (introduced by pthread_cleanup_push) uses a completely
unprotected function pointer on the stack. This function pointer can simplify
the exploitation of stack-based buffer overflows even if the thread in question
is never canceled.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Apparently the name received from the tree walk is not guaranteed to have \0
byte at the end. So let's make sure we append one.
Note that this is only an issue if there are any subvolumes in the container's
rootfs.
Closes 2826.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Callers such as LXD run post-stop hooks to perform cleanup operations on
shutdown. This can involve umount and other things. To avoid surprises with
lingering namespace references we should close all our namespace-preserving
file descriptors. We don't need them at this point anymore anyway.
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
projects / thirdparty / lxc.git / log
