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Trim /proc & /sys subtrees before mounting new instances

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Both /proc and /sys may have sub-mounts in them from the host
OS. We must explicitly unmount them all before mounting the
new instance over that location. If we don't then /proc/mounts
will show the sub-mounts as existing, even though nothing will
be able to access them, due to the over-mount.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2012-05-11 11:35:28 +01:00
parent c16b4c43fc
commit c529b47a75
1 changed files with 47 additions and 14 deletions
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61
src/lxc/lxc_container.c
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@ -1017,26 +1017,29 @@ static int lxcContainerMountAllFS(virDomainDefPtr vmDef,
}
static int lxcContainerUnmountOldFS(void)
static int lxcContainerGetSubtree(const char *prefix,
char ***mountsret,
size_t *nmountsret)
{
struct mntent mntent;
char **mounts = NULL;
int nmounts = 0;
FILE *procmnt;
int i;
struct mntent mntent;
char mntbuf[1024];
int saveErrno;
const char *failedUmount = NULL;
int ret = -1;
char **mounts = NULL;
size_t nmounts = 0;
*mountsret = NULL;
*nmountsret = 0;
if (!(procmnt = setmntent("/proc/mounts", "r"))) {
virReportSystemError(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"))
if (!STRPREFIX(mntent.mnt_dir, prefix))
continue;
if (VIR_REALLOC_N(mounts, nmounts+1) < 0) {
@ -1054,13 +1057,36 @@ static int lxcContainerUnmountOldFS(void)
qsort(mounts, nmounts, sizeof(mounts[0]),
lxcContainerChildMountSort);
*mountsret = mounts;
*nmountsret = nmounts;
ret = 0;
cleanup:
endmntent(procmnt);
return ret;
}
static int lxcContainerUnmountSubtree(const char *prefix,
bool isOldRootFS)
{
char **mounts = NULL;
size_t nmounts = 0;
size_t i;
int saveErrno;
const char *failedUmount = NULL;
int ret = -1;
VIR_DEBUG("Unmount subtreee from %s", prefix);
if (lxcContainerGetSubtree(prefix, &mounts, &nmounts) < 0)
return -1;
for (i = 0 ; i < nmounts ; i++) {
VIR_DEBUG("Umount %s", mounts[i]);
if (umount(mounts[i]) < 0) {
char ebuf[1024];
failedUmount = mounts[i];
saveErrno = errno;
VIR_WARN("Failed to unmount '%s', trying to detach root '%s': %s",
VIR_WARN("Failed to unmount '%s', trying to detach subtree '%s': %s",
failedUmount, mounts[nmounts-1],
virStrerror(errno, ebuf, sizeof(ebuf)));
break;
@ -1068,15 +1094,16 @@ static int lxcContainerUnmountOldFS(void)
}
if (failedUmount) {
/* This detaches the old root filesystem */
/* This detaches the subtree */
if (umount2(mounts[nmounts-1], MNT_DETACH) < 0) {
virReportSystemError(saveErrno,
_("Failed to unmount '%s' and could not detach old root '%s'"),
_("Failed to unmount '%s' and could not detach subtree '%s'"),
failedUmount, mounts[nmounts-1]);
goto cleanup;
}
/* This unmounts the tmpfs on which the old root filesystem was hosted */
if (umount(mounts[nmounts-1]) < 0) {
if (isOldRootFS &&
umount(mounts[nmounts-1]) < 0) {
virReportSystemError(saveErrno,
_("Failed to unmount '%s' and could not unmount old root '%s'"),
failedUmount, mounts[nmounts-1]);
@ -1089,7 +1116,6 @@ static int lxcContainerUnmountOldFS(void)
cleanup:
for (i = 0 ; i < nmounts ; i++)
VIR_FREE(mounts[i]);
endmntent(procmnt);
VIR_FREE(mounts);
return ret;
@ -1127,7 +1153,7 @@ static int lxcContainerSetupPivotRoot(virDomainDefPtr vmDef,
return -1;
/* Gets rid of all remaining mounts from host OS, including /.oldroot itself */
if (lxcContainerUnmountOldFS() < 0)
if (lxcContainerUnmountSubtree("/.oldroot", true) < 0)
return -1;
return 0;
@ -1164,6 +1190,13 @@ static int lxcContainerSetupExtraMounts(virDomainDefPtr vmDef,
if (lxcContainerMountAllFS(vmDef, "", false) < 0)
return -1;
/* Gets rid of any existing stuff under /proc, since we need new
* namespace aware versions of those. We must do /proc second
* otherwise we won't find /proc/mounts :-) */
if (lxcContainerUnmountSubtree("/sys", false) < 0 ||
lxcContainerUnmountSubtree("/proc", false) < 0)
return -1;
/* Mounts the core /proc, /sys, etc filesystems */
if (lxcContainerMountBasicFS(vmDef, false, securityDriver) < 0)
return -1;