[libvirt] [PATCH 4/6] Remove duplicate entries in lxcBasicMounts array
From: "Daniel P. Berrange" <berrange(a)redhat.com>
Currently the lxcBasicMounts array has separate entries for
most mounts, to reflect that we must do a separate mount
operation to make mounts read-only. Remove the duplicate
entries and instead set the MS_RDONLY flag against the main
entry. Then change lxcContainerMountBasicFS to look for the
MS_RDONLY flag, mask it out & do a separate bind mount.
Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com>
---
src/lxc/lxc_container.c | 44 +++++++++++++++++++++++++++-----------------
1 file changed, 27 insertions(+), 17 deletions(-)
diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 1b1c93b..a7f71ef 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -756,22 +756,12 @@ typedef struct {
} virLXCBasicMountInfo;
static const virLXCBasicMountInfo lxcBasicMounts[] = {
- /* When we want to make a bind mount readonly, for unknown reasons,
- * it is currently necessary to bind it once, and then remount the
- * bind with the readonly flag. If this is not done, then the original
- * mount point in the main OS becomes readonly too which is not what
- * we want. Hence some things have two entries here.
- */
{ "proc", "/proc", "proc", MS_NOSUID|MS_NOEXEC|MS_NODEV
},
- { "/proc/sys", "/proc/sys", NULL, MS_BIND },
- { "/proc/sys", "/proc/sys", NULL, MS_BIND|MS_REMOUNT|MS_RDONLY
},
- { "sysfs", "/sys", "sysfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV },
- { "sysfs", "/sys", "sysfs",
MS_BIND|MS_REMOUNT|MS_RDONLY },
- { "securityfs", "/sys/kernel/security", "securityfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV },
- { "securityfs", "/sys/kernel/security", "securityfs",
MS_BIND|MS_REMOUNT|MS_RDONLY },
+ { "/proc/sys", "/proc/sys", NULL, MS_BIND|MS_RDONLY },
+ { "sysfs", "/sys", "sysfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY },
+ { "securityfs", "/sys/kernel/security", "securityfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY },
#if WITH_SELINUX
- { SELINUX_MOUNT, SELINUX_MOUNT, "selinuxfs", MS_NOSUID|MS_NOEXEC|MS_NODEV
},
- { SELINUX_MOUNT, SELINUX_MOUNT, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY },
+ { SELINUX_MOUNT, SELINUX_MOUNT, "selinuxfs",
MS_NOSUID|MS_NOEXEC|MS_NODEV|MS_RDONLY },
#endif
};
@@ -852,6 +842,7 @@ static int lxcContainerMountBasicFS(bool userns_enabled)
VIR_DEBUG("Mounting basic filesystems");
for (i = 0; i < ARRAY_CARDINALITY(lxcBasicMounts); i++) {
+ bool bindOverReadonly;
virLXCBasicMountInfo const *mnt = &lxcBasicMounts[i];
VIR_DEBUG("Processing %s -> %s",
@@ -878,13 +869,32 @@ static int lxcContainerMountBasicFS(bool userns_enabled)
goto cleanup;
}
+ /*
+ * We can't immediately set the MS_RDONLY flag when mounting filesystems
+ * because (in at least some kernel versions) this will propagate back
+ * to the original mount in the host OS, turning it readonly too. This
+ * We mount the filesystem in read-write mode initially, and then do a
+ * separate read-only bind mount on top of that.
+ */
+ bindOverReadonly = !!(mnt->mflags & MS_RDONLY);
+
VIR_DEBUG("Mount %s on %s type=%s flags=%x",
- mnt->src, mnt->dst, mnt->type, mnt->mflags);
- if (mount(mnt->src, mnt->dst, mnt->type, mnt->mflags, NULL) < 0)
{
+ mnt->src, mnt->dst, mnt->type, mnt->mflags &
~MS_RDONLY);
+ if (mount(mnt->src, mnt->dst, mnt->type, mnt->mflags &
~MS_RDONLY, NULL) < 0) {
virReportSystemError(errno,
_("Failed to mount %s on %s type %s
flags=%x"),
mnt->src, mnt->dst, NULLSTR(mnt->type),
- mnt->mflags);
+ mnt->mflags & ~MS_RDONLY);
+ goto cleanup;
+ }
+
+ if (bindOverReadonly &&
+ mount(mnt->src, mnt->dst, NULL,
+ MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0) {
+ virReportSystemError(errno,
+ _("Failed to re-mount %s on %s flags=%x"),
+ mnt->src, mnt->dst,
+ MS_BIND|MS_REMOUNT|MS_RDONLY);
goto cleanup;
}
}
--
1.8.3.1