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Set a security context on /dev and /dev/pts mounts

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To allow the container to access /dev and /dev/pts when under
sVirt, set an explicit mount option. Also set a max size on
the /dev mount to prevent DOS on memory usage

* src/lxc/lxc_container.c: Set /dev mount context
* src/lxc/lxc_controller.c: Set /dev/pts mount context
This commit is contained in:
Daniel P. Berrange 2012-01-25 14:12:54 +00:00 committed by Eric Blake
parent 0f01192e7e
commit 5df67cdcd3
2 changed files with 84 additions and 20 deletions
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72
src/lxc/lxc_container.c
View File

@ -36,6 +36,10 @@
#include <unistd.h> #include <unistd.h>
#include <mntent.h> #include <mntent.h>
#if HAVE_SELINUX
# include <selinux/selinux.h>
#endif
/* Yes, we want linux private one, for _syscall2() macro */ /* Yes, we want linux private one, for _syscall2() macro */
#include <linux/unistd.h> #include <linux/unistd.h>
@ -420,7 +424,6 @@ err:
static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot) static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot)
{ {
const struct { const struct {
bool onlyPivotRoot;
bool needPrefix; bool needPrefix;
const char *src; const char *src;
const char *dst; const char *dst;
@ -434,16 +437,19 @@ static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot)
* mount point in the main OS becomes readonly too which is not what * mount point in the main OS becomes readonly too which is not what
* we want. Hence some things have two entries here. * we want. Hence some things have two entries here.
*/ */
{ true, false, "devfs", "/dev", "tmpfs", "mode=755", MS_NOSUID }, { false, "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV },
{ false, false, "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV }, { false, "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND },
{ false, false, "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND }, { false, "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY },
{ false, false, "/proc/sys", "/proc/sys", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY }, { true, "/sys", "/sys", NULL, NULL, MS_BIND },
{ false, true, "/sys", "/sys", NULL, NULL, MS_BIND }, { true, "/sys", "/sys", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY },
{ false, true, "/sys", "/sys", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY }, { true, "/selinux", "/selinux", NULL, NULL, MS_BIND },
{ false, true, "/selinux", "/selinux", NULL, NULL, MS_BIND }, { true, "/selinux", "/selinux", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY },
{ false, true, "/selinux", "/selinux", NULL, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY },
}; };
int i, rc = -1; int i, rc = -1;
char *opts = NULL;
#if HAVE_SELINUX
security_context_t con;
#endif
VIR_DEBUG("Mounting basic filesystems %s pivotRoot=%d", NULLSTR(srcprefix), pivotRoot); VIR_DEBUG("Mounting basic filesystems %s pivotRoot=%d", NULLSTR(srcprefix), pivotRoot);
@ -451,10 +457,8 @@ static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot)
char *src = NULL; char *src = NULL;
const char *srcpath = NULL; const char *srcpath = NULL;
VIR_DEBUG("Consider %s onlyPivotRoot=%d", VIR_DEBUG("Processing %s -> %s",
mnts[i].src, mnts[i].onlyPivotRoot); mnts[i].src, mnts[i].dst);
if (mnts[i].onlyPivotRoot && !pivotRoot)
continue;
if (virFileMakePath(mnts[i].dst) < 0) { if (virFileMakePath(mnts[i].dst) < 0) {
virReportSystemError(errno, virReportSystemError(errno,
@ -475,8 +479,10 @@ static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot)
/* Skip if mount doesn't exist in source */ /* Skip if mount doesn't exist in source */
if ((srcpath[0] == '/') && if ((srcpath[0] == '/') &&
(access(srcpath, R_OK) < 0)) (access(srcpath, R_OK) < 0)) {
VIR_FREE(src);
continue; continue;
}
VIR_DEBUG("Mount %s on %s type=%s flags=%x, opts=%s", VIR_DEBUG("Mount %s on %s type=%s flags=%x, opts=%s",
srcpath, mnts[i].dst, mnts[i].type, mnts[i].mflags, mnts[i].opts); srcpath, mnts[i].dst, mnts[i].type, mnts[i].mflags, mnts[i].opts);
@ -490,15 +496,47 @@ static int lxcContainerMountBasicFS(const char *srcprefix, bool pivotRoot)
VIR_FREE(src); VIR_FREE(src);
} }
if (pivotRoot) {
#if HAVE_SELINUX
if (getfilecon("/", &con) < 0 &&
errno != ENOTSUP) {
virReportSystemError(errno, "%s",
_("Failed to query file context on /"));
goto cleanup;
}
#endif
/*
* tmpfs is limited to 64kb, since we only have device nodes in there
* and don't want to DOS the entire OS RAM usage
*/
if (virAsprintf(&opts, "mode=755,size=65536%s%s%s",
con ? ",context=\"" : "",
con ? (const char *)con : "",
con ? "\"" : "") < 0) {
virReportOOMError();
goto cleanup;
}
VIR_DEBUG("Mount devfs on /dev type=tmpfs flags=%x, opts=%s",
MS_NOSUID, opts);
if (mount("devfs", "/dev", "tmpfs", MS_NOSUID, opts) < 0) {
virReportSystemError(errno,
_("Failed to mount %s on %s type %s"),
"devfs", "/dev", "tmpfs");
goto cleanup;
}
}
rc = 0; rc = 0;
cleanup: cleanup:
VIR_DEBUG("rc=%d", rc); VIR_DEBUG("rc=%d", rc);
VIR_FREE(opts);
return rc; return rc;
} }
static int lxcContainerMountDevFS(virDomainFSDefPtr root) static int lxcContainerMountFSDevPTS(virDomainFSDefPtr root)
{ {
char *devpts = NULL; char *devpts = NULL;
int rc = -1; int rc = -1;
@ -1070,8 +1108,8 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
if (lxcContainerMountBasicFS("/.oldroot", true) < 0) if (lxcContainerMountBasicFS("/.oldroot", true) < 0)
return -1; return -1;
/* Mounts /dev and /dev/pts */ /* Mounts /dev/pts */
if (lxcContainerMountDevFS(root) < 0) if (lxcContainerMountFSDevPTS(root) < 0)
return -1; return -1;
/* Populates device nodes in /dev/ */ /* Populates device nodes in /dev/ */

32
src/lxc/lxc_controller.c
View File

@ -52,6 +52,9 @@
# define NUMA_VERSION1_COMPATIBILITY 1 # define NUMA_VERSION1_COMPATIBILITY 1
# include <numa.h> # include <numa.h>
#endif #endif
#if HAVE_SELINUX
# include <selinux/selinux.h>
#endif
#include "virterror_internal.h" #include "virterror_internal.h"
#include "logging.h" #include "logging.h"
@ -1433,6 +1436,10 @@ lxcControllerRun(virDomainDefPtr def,
* marked as shared * marked as shared
*/ */
if (root) { if (root) {
#if HAVE_SELINUX
security_context_t con;
#endif
char *opts;
VIR_DEBUG("Setting up private /dev/pts"); VIR_DEBUG("Setting up private /dev/pts");
if (!virFileExists(root->src)) { if (!virFileExists(root->src)) {
@ -1467,16 +1474,35 @@ lxcControllerRun(virDomainDefPtr def,
goto cleanup; goto cleanup;
} }
#if HAVE_SELINUX
if (getfilecon(root->src, &con) < 0 &&
errno != ENOTSUP) {
virReportSystemError(errno,
_("Failed to query file context on %s"),
root->src);
goto cleanup;
}
#endif
/* XXX should we support gid=X for X!=5 for distros which use /* XXX should we support gid=X for X!=5 for distros which use
* a different gid for tty? */ * a different gid for tty? */
VIR_DEBUG("Mounting 'devpts' on %s", devpts); if (virAsprintf(&opts, "newinstance,ptmxmode=0666,mode=0620,gid=5%s%s%s",
if (mount("devpts", devpts, "devpts", 0, con ? ",context=\"" : "",
"newinstance,ptmxmode=0666,mode=0620,gid=5") < 0) { con ? (const char *)con : "",
con ? "\"" : "") < 0) {
virReportOOMError();
goto cleanup;
}
VIR_DEBUG("Mount devpts on %s type=tmpfs flags=%x, opts=%s",
devpts, MS_NOSUID, opts);
if (mount("devpts", devpts, "devpts", MS_NOSUID, opts) < 0) {
VIR_FREE(opts);
virReportSystemError(errno, virReportSystemError(errno,
_("Failed to mount devpts on %s"), _("Failed to mount devpts on %s"),
devpts); devpts);
goto cleanup; goto cleanup;
} }
VIR_FREE(opts);
if (access(devptmx, R_OK) < 0) { if (access(devptmx, R_OK) < 0) {
VIR_WARN("Kernel does not support private devpts, using shared devpts"); VIR_WARN("Kernel does not support private devpts, using shared devpts");