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libvirt/src/lxc_container.c
Daniel P. Berrange eb6d21cc0e Reduce LXC capabilities
2009-06-29 17:09:42 +00:00

861 lines
23 KiB
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/*
* Copyright IBM Corp. 2008
* Copyright Red Hat 2008
*
* lxc_container.c: file description
*
* Authors:
* David L. Leskovec <dlesko at linux.vnet.ibm.com>
* Daniel P. Berrange <berrange@redhat.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <config.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/wait.h>
#include <unistd.h>
#include <mntent.h>
/* Yes, we want linux private one, for _syscall2() macro */
#include <linux/unistd.h>
/* For MS_MOVE */
#include <linux/fs.h>
#if HAVE_CAPNG
#include <cap-ng.h>
#endif
#include "virterror_internal.h"
#include "logging.h"
#include "lxc_container.h"
#include "util.h"
#include "memory.h"
#include "veth.h"
#define VIR_FROM_THIS VIR_FROM_LXC
/*
* GLibc headers are behind the kernel, so we define these
* constants if they're not present already.
*/
#ifndef CLONE_NEWPID
#define CLONE_NEWPID 0x20000000
#endif
#ifndef CLONE_NEWUTS
#define CLONE_NEWUTS 0x04000000
#endif
#ifndef CLONE_NEWUSER
#define CLONE_NEWUSER 0x10000000
#endif
#ifndef CLONE_NEWIPC
#define CLONE_NEWIPC 0x08000000
#endif
#ifndef CLONE_NEWNET
#define CLONE_NEWNET 0x40000000 /* New network namespace */
#endif
/* messages between parent and container */
typedef char lxc_message_t;
#define LXC_CONTINUE_MSG 'c'
typedef struct __lxc_child_argv lxc_child_argv_t;
struct __lxc_child_argv {
virDomainDefPtr config;
unsigned int nveths;
char **veths;
int monitor;
char *ttyPath;
};
/**
* lxcContainerExecInit:
* @vmDef: Ptr to vm definition structure
*
* Exec the container init string. The container init will replace then
* be running in the current process
*
* Does not return
*/
static int lxcContainerExecInit(virDomainDefPtr vmDef)
{
const char *const argv[] = {
vmDef->os.init,
NULL,
};
return execve(argv[0], (char **)argv, NULL);
}
/**
* lxcContainerSetStdio:
* @control: the conrol FD
* @ttyPath: Name of tty to set as the container console
*
* Sets the given tty as the primary conosole for the container as well as
* stdout, stdin and stderr.
*
* Returns 0 on success or -1 in case of error
*/
static int lxcContainerSetStdio(int control, int ttyfd)
{
int rc = -1;
int open_max, i;
if (setsid() < 0) {
virReportSystemError(NULL, errno, "%s",
_("setsid failed"));
goto cleanup;
}
if (ioctl(ttyfd, TIOCSCTTY, NULL) < 0) {
virReportSystemError(NULL, errno, "%s",
_("ioctl(TIOCSTTY) failed"));
goto cleanup;
}
/* Just in case someone forget to set FD_CLOEXEC, explicitly
* close all FDs before executing the container */
open_max = sysconf (_SC_OPEN_MAX);
for (i = 0; i < open_max; i++)
if (i != ttyfd && i != control)
close(i);
if (dup2(ttyfd, 0) < 0) {
virReportSystemError(NULL, errno, "%s",
_("dup2(stdin) failed"));
goto cleanup;
}
if (dup2(ttyfd, 1) < 0) {
virReportSystemError(NULL, errno, "%s",
_("dup2(stdout) failed"));
goto cleanup;
}
if (dup2(ttyfd, 2) < 0) {
virReportSystemError(NULL, errno, "%s",
_("dup2(stderr) failed"));
goto cleanup;
}
rc = 0;
cleanup:
return rc;
}
/**
* lxcContainerSendContinue:
* @monitor: control FD to child
*
* Sends the continue message via the socket pair stored in the vm
* structure.
*
* Returns 0 on success or -1 in case of error
*/
int lxcContainerSendContinue(int control)
{
int rc = -1;
lxc_message_t msg = LXC_CONTINUE_MSG;
int writeCount = 0;
writeCount = safewrite(control, &msg, sizeof(msg));
if (writeCount != sizeof(msg)) {
virReportSystemError(NULL, errno, "%s",
_("unable to send container continue message"));
goto error_out;
}
rc = 0;
error_out:
return rc;
}
/**
* lxcContainerWaitForContinue:
* @control: control FD from parent
*
* This function will wait for the container continue message from the
* parent process. It will send this message on the socket pair stored in
* the vm structure once it has completed the post clone container setup.
*
* Returns 0 on success or -1 in case of error
*/
static int lxcContainerWaitForContinue(int control)
{
lxc_message_t msg;
int readLen;
readLen = saferead(control, &msg, sizeof(msg));
if (readLen != sizeof(msg) ||
msg != LXC_CONTINUE_MSG) {
virReportSystemError(NULL, errno, "%s",
_("Failed to read the container continue message"));
return -1;
}
close(control);
DEBUG0("Received container continue message");
return 0;
}
/**
* lxcEnableInterfaces:
* @vm: Pointer to vm structure
*
* This function will enable the interfaces for this container.
*
* Returns 0 on success or nonzero in case of error
*/
static int lxcContainerEnableInterfaces(unsigned int nveths,
char **veths)
{
int rc = 0;
unsigned int i;
for (i = 0 ; i < nveths ; i++) {
DEBUG("Enabling %s", veths[i]);
rc = vethInterfaceUpOrDown(veths[i], 1);
if (0 != rc) {
goto error_out;
}
}
/* enable lo device only if there were other net devices */
if (veths)
rc = vethInterfaceUpOrDown("lo", 1);
error_out:
return rc;
}
//_syscall2(int, pivot_root, char *, newroot, const char *, oldroot)
extern int pivot_root(const char * new_root,const char * put_old);
static int lxcContainerChildMountSort(const void *a, const void *b)
{
const char **sa = (const char**)a;
const char **sb = (const char**)b;
/* Delibrately reversed args - we need to unmount deepest
children first */
return strcmp(*sb, *sa);
}
#ifndef MS_REC
#define MS_REC 16384
#endif
#ifndef MNT_DETACH
#define MNT_DETACH 0x00000002
#endif
#ifndef MS_PRIVATE
#define MS_PRIVATE (1<<18)
#endif
#ifndef MS_SLAVE
#define MS_SLAVE (1<<19)
#endif
static int lxcContainerPivotRoot(virDomainFSDefPtr root)
{
int rc, ret;
char *oldroot = NULL, *newroot = NULL;
ret = -1;
/* root->parent must be private, so make / private. */
if (mount("", "/", NULL, MS_PRIVATE|MS_REC, NULL) < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to make root private"));
goto err;
}
if (virAsprintf(&oldroot, "%s/.oldroot", root->src) < 0) {
virReportOOMError(NULL);
goto err;
}
if ((rc = virFileMakePath(oldroot)) < 0) {
virReportSystemError(NULL, rc,
_("failed to create %s"),
oldroot);
goto err;
}
/* Create a tmpfs root since old and new roots must be
* on separate filesystems */
if (mount("tmprootfs", oldroot, "tmpfs", 0, NULL) < 0) {
virReportSystemError(NULL, errno,
_("failed to mount empty tmpfs at %s"),
oldroot);
goto err;
}
/* Create a directory called 'new' in tmpfs */
if (virAsprintf(&newroot, "%s/new", oldroot) < 0) {
virReportOOMError(NULL);
goto err;
}
if ((rc = virFileMakePath(newroot)) < 0) {
virReportSystemError(NULL, rc,
_("failed to create %s"),
newroot);
goto err;
}
/* ... and mount our root onto it */
if (mount(root->src, newroot, NULL, MS_BIND|MS_REC, NULL) < 0) {
virReportSystemError(NULL, errno,
_("failed to bind new root %s into tmpfs"),
root->src);
goto err;
}
/* Now we chroot into the tmpfs, then pivot into the
* root->src bind-mounted onto '/new' */
if (chdir(newroot) < 0) {
virReportSystemError(NULL, errno,
_("failed to chroot into %s"), newroot);
goto err;
}
/* The old root directory will live at /.oldroot after
* this and will soon be unmounted completely */
if (pivot_root(".", ".oldroot") < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to pivot root"));
goto err;
}
/* CWD is undefined after pivot_root, so go to / */
if (chdir("/") < 0)
goto err;
ret = 0;
err:
VIR_FREE(oldroot);
VIR_FREE(newroot);
return ret;
}
static int lxcContainerMountBasicFS(virDomainFSDefPtr root)
{
const struct {
const char *src;
const char *dst;
const char *type;
} mnts[] = {
{ "/dev", "/dev", "tmpfs" },
{ "/proc", "/proc", "proc" },
{ "/sys", "/sys", "sysfs" },
#if WITH_SELINUX
{ "none", "/selinux", "selinuxfs" },
#endif
};
int i, rc;
char *devpts;
if (virAsprintf(&devpts, "/.oldroot%s/dev/pts", root->src) < 0) {
virReportOOMError(NULL);
return -1;
}
for (i = 0 ; i < ARRAY_CARDINALITY(mnts) ; i++) {
if (virFileMakePath(mnts[i].dst) < 0) {
virReportSystemError(NULL, errno,
_("failed to mkdir %s"),
mnts[i].src);
return -1;
}
if (mount(mnts[i].src, mnts[i].dst, mnts[i].type, 0, NULL) < 0) {
virReportSystemError(NULL, errno,
_("failed to mount %s on %s"),
mnts[i].type, mnts[i].type);
return -1;
}
}
if ((rc = virFileMakePath("/dev/pts") < 0)) {
virReportSystemError(NULL, rc, "%s",
_("cannot create /dev/pts"));
return -1;
}
VIR_DEBUG("Trying to move %s to %s", devpts, "/dev/pts");
if ((rc = mount(devpts, "/dev/pts", NULL, MS_MOVE, NULL)) < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to mount /dev/pts in container"));
return -1;
}
VIR_FREE(devpts);
return 0;
}
static int lxcContainerPopulateDevices(void)
{
int i;
const struct {
int maj;
int min;
mode_t mode;
const char *path;
} devs[] = {
{ LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_NULL, 0666, "/dev/null" },
{ LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_ZERO, 0666, "/dev/zero" },
{ LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_FULL, 0666, "/dev/full" },
{ LXC_DEV_MAJ_TTY, LXC_DEV_MIN_CONSOLE, 0600, "/dev/console" },
{ LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_RANDOM, 0666, "/dev/random" },
{ LXC_DEV_MAJ_MEMORY, LXC_DEV_MIN_URANDOM, 0666, "/dev/urandom" },
};
/* Populate /dev/ with a few important bits */
for (i = 0 ; i < ARRAY_CARDINALITY(devs) ; i++) {
dev_t dev = makedev(devs[i].maj, devs[i].min);
if (mknod(devs[i].path, S_IFCHR, dev) < 0 ||
chmod(devs[i].path, devs[i].mode)) {
virReportSystemError(NULL, errno,
_("failed to make device %s"),
devs[i].path);
return -1;
}
}
if (access("/dev/pts/ptmx", W_OK) == 0) {
if (symlink("/dev/pts/ptmx", "/dev/ptmx") < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to create symlink /dev/ptmx to /dev/pts/ptmx"));
return -1;
}
} else {
dev_t dev = makedev(LXC_DEV_MAJ_TTY, LXC_DEV_MIN_PTMX);
if (mknod("/dev/ptmx", S_IFCHR, dev) < 0 ||
chmod("/dev/ptmx", 0666)) {
virReportSystemError(NULL, errno, "%s",
_("failed to make device /dev/ptmx"));
return -1;
}
}
return 0;
}
static int lxcContainerMountNewFS(virDomainDefPtr vmDef)
{
int i;
/* Pull in rest of container's mounts */
for (i = 0 ; i < vmDef->nfss ; i++) {
char *src;
if (STREQ(vmDef->fss[i]->dst, "/"))
continue;
// XXX fix
if (vmDef->fss[i]->type != VIR_DOMAIN_FS_TYPE_MOUNT)
continue;
if (virAsprintf(&src, "/.oldroot/%s", vmDef->fss[i]->src) < 0) {
virReportOOMError(NULL);
return -1;
}
if (virFileMakePath(vmDef->fss[i]->dst) < 0) {
virReportSystemError(NULL, errno,
_("failed to create %s"),
vmDef->fss[i]->dst);
VIR_FREE(src);
return -1;
}
if (mount(src, vmDef->fss[i]->dst, NULL, MS_BIND, NULL) < 0) {
VIR_FREE(src);
virReportSystemError(NULL, errno,
_("failed to mount %s at %s"),
vmDef->fss[i]->src,
vmDef->fss[i]->dst);
return -1;
}
VIR_FREE(src);
}
return 0;
}
static int lxcContainerUnmountOldFS(void)
{
struct mntent mntent;
char **mounts = NULL;
int nmounts = 0;
FILE *procmnt;
int i;
char mntbuf[1024];
if (!(procmnt = setmntent("/proc/mounts", "r"))) {
virReportSystemError(NULL, errno, "%s",
_("failed to read /proc/mounts"));
return -1;
}
while (getmntent_r(procmnt, &mntent, mntbuf, sizeof(mntbuf)) != NULL) {
VIR_DEBUG("Got %s", mntent.mnt_dir);
if (!STRPREFIX(mntent.mnt_dir, "/.oldroot"))
continue;
if (VIR_REALLOC_N(mounts, nmounts+1) < 0) {
endmntent(procmnt);
virReportOOMError(NULL);
return -1;
}
if (!(mounts[nmounts++] = strdup(mntent.mnt_dir))) {
endmntent(procmnt);
virReportOOMError(NULL);
return -1;
}
}
endmntent(procmnt);
qsort(mounts, nmounts, sizeof(mounts[0]),
lxcContainerChildMountSort);
for (i = 0 ; i < nmounts ; i++) {
VIR_DEBUG("Umount %s", mounts[i]);
if (umount(mounts[i]) < 0) {
virReportSystemError(NULL, errno,
_("failed to unmount '%s'"),
mounts[i]);
return -1;
}
VIR_FREE(mounts[i]);
}
VIR_FREE(mounts);
return 0;
}
/* Got a FS mapped to /, we're going the pivot_root
* approach to do a better-chroot-than-chroot
* this is based on this thread http://lkml.org/lkml/2008/3/5/29
*/
static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
virDomainFSDefPtr root)
{
/* Gives us a private root, leaving all parent OS mounts on /.oldroot */
if (lxcContainerPivotRoot(root) < 0)
return -1;
/* Mounts the core /proc, /sys, /dev, /dev/pts filesystems */
if (lxcContainerMountBasicFS(root) < 0)
return -1;
/* Populates device nodes in /dev/ */
if (lxcContainerPopulateDevices() < 0)
return -1;
/* Sets up any non-root mounts from guest config */
if (lxcContainerMountNewFS(vmDef) < 0)
return -1;
/* Gets rid of all remaining mounts from host OS, including /.oldroot itself */
if (lxcContainerUnmountOldFS() < 0)
return -1;
return 0;
}
/* Nothing mapped to /, we're using the main root,
but with extra stuff mapped in */
static int lxcContainerSetupExtraMounts(virDomainDefPtr vmDef)
{
int i;
if (mount("", "/", NULL, MS_SLAVE|MS_REC, NULL) < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to make / slave"));
return -1;
}
for (i = 0 ; i < vmDef->nfss ; i++) {
// XXX fix to support other mount types
if (vmDef->fss[i]->type != VIR_DOMAIN_FS_TYPE_MOUNT)
continue;
if (mount(vmDef->fss[i]->src,
vmDef->fss[i]->dst,
NULL,
MS_BIND,
NULL) < 0) {
virReportSystemError(NULL, errno,
_("failed to mount %s at %s"),
vmDef->fss[i]->src,
vmDef->fss[i]->dst);
return -1;
}
}
/* mount /proc */
if (mount("lxcproc", "/proc", "proc", 0, NULL) < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to mount /proc"));
return -1;
}
return 0;
}
static int lxcContainerSetupMounts(virDomainDefPtr vmDef,
virDomainFSDefPtr root)
{
if (root)
return lxcContainerSetupPivotRoot(vmDef, root);
else
return lxcContainerSetupExtraMounts(vmDef);
}
/*
* This is running as the 'init' process insid the container.
* It removes some capabilities that could be dangerous to
* host system, since they are not currently "containerized"
*/
static int lxcContainerDropCapabilities(void)
{
#if HAVE_CAPNG
int ret;
capng_get_caps_process();
if ((ret = capng_updatev(CAPNG_DROP,
CAPNG_EFFECTIVE | CAPNG_PERMITTED |
CAPNG_INHERITABLE | CAPNG_BOUNDING_SET,
CAP_SYS_BOOT, /* No use of reboot */
CAP_SYS_MODULE, /* No kernel module loading */
CAP_SYS_TIME, /* No changing the clock */
CAP_AUDIT_CONTROL, /* No messing with auditing status */
CAP_MAC_ADMIN, /* No messing with LSM config */
-1 /* sentinal */)) < 0) {
lxcError(NULL, NULL, VIR_ERR_INTERNAL_ERROR,
_("failed to remove capabilities %d"), ret);
return -1;
}
if ((ret = capng_apply(CAPNG_SELECT_BOTH)) < 0) {
lxcError(NULL, NULL, VIR_ERR_INTERNAL_ERROR,
_("failed to apply capabilities: %d"), ret);
return -1;
}
/* Need to prevent them regaining any caps on exec */
if ((ret = capng_lock()) < 0) {
lxcError(NULL, NULL, VIR_ERR_INTERNAL_ERROR,
_("failed to lock capabilities: %d"), ret);
return -1;
}
#else
VIR_WARN0(_("libcap-ng support not compiled in, unable to clear capabilities"));
#endif
return 0;
}
/**
* lxcChild:
* @argv: Pointer to container arguments
*
* This function is run in the process clone()'d in lxcStartContainer.
* Perform a number of container setup tasks:
* Setup container file system
* mount container /proca
* Then exec's the container init
*
* Returns 0 on success or -1 in case of error
*/
static int lxcContainerChild( void *data )
{
lxc_child_argv_t *argv = data;
virDomainDefPtr vmDef = argv->config;
int ttyfd;
char *ttyPath;
virDomainFSDefPtr root;
if (NULL == vmDef) {
lxcError(NULL, NULL, VIR_ERR_INTERNAL_ERROR,
"%s", _("lxcChild() passed invalid vm definition"));
return -1;
}
root = virDomainGetRootFilesystem(vmDef);
if (root) {
if (virAsprintf(&ttyPath, "%s%s", root->src, argv->ttyPath) < 0) {
virReportOOMError(NULL);
return -1;
}
} else {
if (!(ttyPath = strdup(argv->ttyPath))) {
virReportOOMError(NULL);
return -1;
}
}
ttyfd = open(ttyPath, O_RDWR|O_NOCTTY);
if (ttyfd < 0) {
virReportSystemError(NULL, errno,
_("failed to open tty %s"),
ttyPath);
return -1;
}
VIR_FREE(ttyPath);
if (lxcContainerSetStdio(argv->monitor, ttyfd) < 0) {
close(ttyfd);
return -1;
}
close(ttyfd);
if (lxcContainerSetupMounts(vmDef, root) < 0)
return -1;
/* Wait for interface devices to show up */
if (lxcContainerWaitForContinue(argv->monitor) < 0)
return -1;
/* enable interfaces */
if (lxcContainerEnableInterfaces(argv->nveths, argv->veths) < 0)
return -1;
/* drop a set of root capabilities */
if (lxcContainerDropCapabilities() < 0)
return -1;
/* this function will only return if an error occured */
return lxcContainerExecInit(vmDef);
}
static int userns_supported(void)
{
return lxcContainerAvailable(LXC_CONTAINER_FEATURE_USER) == 0;
}
/**
* lxcContainerStart:
* @driver: pointer to driver structure
* @vm: pointer to virtual machine structure
*
* Starts a container process by calling clone() with the namespace flags
*
* Returns PID of container on success or -1 in case of error
*/
int lxcContainerStart(virDomainDefPtr def,
unsigned int nveths,
char **veths,
int control,
char *ttyPath)
{
pid_t pid;
int flags;
int stacksize = getpagesize() * 4;
char *stack, *stacktop;
lxc_child_argv_t args = { def, nveths, veths, control, ttyPath };
/* allocate a stack for the container */
if (VIR_ALLOC_N(stack, stacksize) < 0) {
virReportOOMError(NULL);
return -1;
}
stacktop = stack + stacksize;
flags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|SIGCHLD;
if (userns_supported())
flags |= CLONE_NEWUSER;
if (def->nets != NULL)
flags |= CLONE_NEWNET;
pid = clone(lxcContainerChild, stacktop, flags, &args);
VIR_FREE(stack);
DEBUG("clone() returned, %d", pid);
if (pid < 0) {
virReportSystemError(NULL, errno, "%s",
_("failed to run clone container"));
return -1;
}
return pid;
}
static int lxcContainerDummyChild(void *argv ATTRIBUTE_UNUSED)
{
_exit(0);
}
int lxcContainerAvailable(int features)
{
int flags = CLONE_NEWPID|CLONE_NEWNS|CLONE_NEWUTS|
CLONE_NEWIPC|SIGCHLD;
int cpid;
char *childStack;
char *stack;
int childStatus;
if (features & LXC_CONTAINER_FEATURE_USER)
flags |= CLONE_NEWUSER;
if (features & LXC_CONTAINER_FEATURE_NET)
flags |= CLONE_NEWNET;
if (VIR_ALLOC_N(stack, getpagesize() * 4) < 0) {
DEBUG0("Unable to allocate stack");
return -1;
}
childStack = stack + (getpagesize() * 4);
cpid = clone(lxcContainerDummyChild, childStack, flags, NULL);
VIR_FREE(stack);
if (cpid < 0) {
char ebuf[1024];
DEBUG("clone call returned %s, container support is not enabled",
virStrerror(errno, ebuf, sizeof ebuf));
return -1;
} else {
waitpid(cpid, &childStatus, 0);
}
return 0;
}
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