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authorEric W. Biederman <ebiederm@xmission.com>2013-03-30 08:04:39 +0400
committerEric W. Biederman <ebiederm@xmission.com>2013-07-24 20:14:46 +0400
commit5ff9d8a65ce80efb509ce4e8051394e9ed2cd942 (patch)
treee2ae0447cda004f29a2a081bbdb428a72862402b /include/linux/mount.h
parentad81f0545ef01ea651886dddac4bef6cec930092 (diff)
downloadlinux-5ff9d8a65ce80efb509ce4e8051394e9ed2cd942.tar.xz
vfs: Lock in place mounts from more privileged users
When creating a less privileged mount namespace or propogating mounts from a more privileged to a less privileged mount namespace lock the submounts so they may not be unmounted individually in the child mount namespace revealing what is under them. This enforces the reasonable expectation that it is not possible to see under a mount point. Most of the time mounts are on empty directories and revealing that does not matter, however I have seen an occassionaly sloppy configuration where there were interesting things concealed under a mount point that probably should not be revealed. Expirable submounts are not locked because they will eventually unmount automatically so whatever is under them already needs to be safe for unprivileged users to access. From a practical standpoint these restrictions do not appear to be significant for unprivileged users of the mount namespace. Recursive bind mounts and pivot_root continues to work, and mounts that are created in a mount namespace may be unmounted there. All of which means that the common idiom of keeping a directory of interesting files and using pivot_root to throw everything else away continues to work just fine. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'include/linux/mount.h')
-rw-r--r--include/linux/mount.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 73005f9957ea..38cd98f112a0 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -48,6 +48,7 @@ struct mnt_namespace;
#define MNT_INTERNAL 0x4000
#define MNT_LOCK_READONLY 0x400000
+#define MNT_LOCKED 0x800000
struct vfsmount {
struct dentry *mnt_root; /* root of the mounted tree */