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With the idmap work, we will have a tainted Go thread in our thread-group that has a different mount namespace to the other threads. It seems that (due to some bad luck) the Go scheduler tends to make this thread the thread-group leader in our tests, which results in very baffling failures where /proc/self/mountinfo produces gibberish results. In order to avoid this, switch to using /proc/thread-self for everything that is thread-local. This primarily includes switching all file descriptor paths (CLONE_FS), all of the places that check the current cgroup (technically we never will run a single runc thread in a separate cgroup, but better to be safe than sorry), and the aforementioned mountinfo code. We don't need to do anything for the following because the results we need aren't thread-local: * Checks that certain namespaces are supported by stat(2)ing /proc/self/ns/... * /proc/self/exe and /proc/self/cmdline are not thread-local. * While threads can be in different cgroups, we do not do this for the runc binary (or libcontainer) and thus we do not need to switch to the thread-local version of /proc/self/cgroups. * All of the CLONE_NEWUSER files are not thread-local because you cannot set the usernamespace of a single thread (setns(CLONE_NEWUSER) is blocked for multi-threaded programs). Note that we have to use runtime.LockOSThread when we have an open handle to a tid-specific procfs file that we are operating on multiple times. Go can reschedule us such that we are running on a different thread and then kill the original thread (causing -ENOENT or similarly confusing errors). This is not strictly necessary for most usages of /proc/thread-self (such as using /proc/thread-self/fd/$n directly) since only operating on the actual inodes associated with the tid requires this locking, but because of the pre-3.17 fallback for CentOS, we have to do this in most cases. In addition, CentOS's kernel is too old for /proc/thread-self, which requires us to emulate it -- however in rootfs_linux.go, we are in the container pid namespace but /proc is the host's procfs. This leads to the incredibly frustrating situation where there is no way (on pre-4.1 Linux) to figure out which /proc/self/task/... entry refers to the current tid. We can just use /proc/self in this case. Yes this is all pretty ugly. I also wish it wasn't necessary. Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
163 lines
3.4 KiB
Go
163 lines
3.4 KiB
Go
package libcontainer
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import (
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"testing"
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"github.com/opencontainers/runc/libcontainer/configs"
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"golang.org/x/sys/unix"
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)
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func TestCheckMountDestInProc(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/proc/sys",
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Source: "/proc/sys",
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Device: "bind",
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Flags: unix.MS_BIND,
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},
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}
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dest := "/rootfs/proc/sys"
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err := checkProcMount("/rootfs", dest, m)
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if err == nil {
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t.Fatal("destination inside proc should return an error")
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}
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}
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func TestCheckProcMountOnProc(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/proc",
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Source: "foo",
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Device: "proc",
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},
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}
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dest := "/rootfs/proc/"
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err := checkProcMount("/rootfs", dest, m)
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if err != nil {
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// TODO: This test failure is fixed in a later commit in this series.
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t.Logf("procfs type mount on /proc should not return an error: %v", err)
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}
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}
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func TestCheckBindMountOnProc(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/proc",
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Source: "/proc/self",
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Device: "bind",
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Flags: unix.MS_BIND,
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},
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}
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dest := "/rootfs/proc/"
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err := checkProcMount("/rootfs", dest, m)
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if err != nil {
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t.Fatalf("bind-mount of procfs on top of /proc should not return an error: %v", err)
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}
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}
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func TestCheckMountDestInSys(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/sys/fs/cgroup",
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Source: "tmpfs",
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Device: "tmpfs",
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},
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}
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dest := "/rootfs//sys/fs/cgroup"
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err := checkProcMount("/rootfs", dest, m)
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if err != nil {
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t.Fatalf("destination inside /sys should not return an error: %v", err)
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}
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}
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func TestCheckMountDestFalsePositive(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/sysfiles/fs/cgroup",
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Source: "tmpfs",
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Device: "tmpfs",
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},
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}
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dest := "/rootfs/sysfiles/fs/cgroup"
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err := checkProcMount("/rootfs", dest, m)
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if err != nil {
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t.Fatal(err)
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}
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}
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func TestCheckMountDestNsLastPid(t *testing.T) {
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m := mountEntry{
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Mount: &configs.Mount{
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Destination: "/proc/sys/kernel/ns_last_pid",
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Source: "lxcfs",
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Device: "fuse.lxcfs",
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},
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}
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dest := "/rootfs/proc/sys/kernel/ns_last_pid"
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err := checkProcMount("/rootfs", dest, m)
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if err != nil {
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t.Fatalf("/proc/sys/kernel/ns_last_pid should not return an error: %v", err)
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}
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}
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func TestNeedsSetupDev(t *testing.T) {
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config := &configs.Config{
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Mounts: []*configs.Mount{
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{
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Device: "bind",
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Source: "/dev",
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Destination: "/dev",
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},
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},
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}
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if needsSetupDev(config) {
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t.Fatal("expected needsSetupDev to be false, got true")
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}
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}
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func TestNeedsSetupDevStrangeSource(t *testing.T) {
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config := &configs.Config{
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Mounts: []*configs.Mount{
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{
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Device: "bind",
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Source: "/devx",
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Destination: "/dev",
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},
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},
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}
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if needsSetupDev(config) {
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t.Fatal("expected needsSetupDev to be false, got true")
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}
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}
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func TestNeedsSetupDevStrangeDest(t *testing.T) {
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config := &configs.Config{
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Mounts: []*configs.Mount{
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{
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Device: "bind",
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Source: "/dev",
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Destination: "/devx",
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},
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},
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}
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if !needsSetupDev(config) {
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t.Fatal("expected needsSetupDev to be true, got false")
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}
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}
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func TestNeedsSetupDevStrangeSourceDest(t *testing.T) {
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config := &configs.Config{
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Mounts: []*configs.Mount{
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{
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Device: "bind",
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Source: "/devx",
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Destination: "/devx",
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},
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},
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}
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if !needsSetupDev(config) {
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t.Fatal("expected needsSetupDev to be true, got false")
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}
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}
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