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authorEric W. Biederman <ebiederm@xmission.com>2013-03-22 04:08:05 -0700
committerEric W. Biederman <ebiederm@xmission.com>2013-03-27 07:50:05 -0700
commit132c94e31b8bca8ea921f9f96a57d684fa4ae0a9 (patch)
tree52db12073a31f62301367416b2a3afec185975ef /fs/pnode.c
parent90563b198e4c6674c63672fae1923da467215f45 (diff)
vfs: Carefully propogate mounts across user namespaces
As a matter of policy MNT_READONLY should not be changable if the original mounter had more privileges than creator of the mount namespace. Add the flag CL_UNPRIVILEGED to note when we are copying a mount from a mount namespace that requires more privileges to a mount namespace that requires fewer privileges. When the CL_UNPRIVILEGED flag is set cause clone_mnt to set MNT_NO_REMOUNT if any of the mnt flags that should never be changed are set. This protects both mount propagation and the initial creation of a less privileged mount namespace. Cc: stable@vger.kernel.org Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'fs/pnode.c')
-rw-r--r--fs/pnode.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
index 3e000a51ac0..8b29d2164da 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -9,6 +9,7 @@
#include <linux/mnt_namespace.h>
#include <linux/mount.h>
#include <linux/fs.h>
+#include <linux/nsproxy.h>
#include "internal.h"
#include "pnode.h"
@@ -220,6 +221,7 @@ static struct mount *get_source(struct mount *dest,
int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
struct mount *source_mnt, struct list_head *tree_list)
{
+ struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
struct mount *m, *child;
int ret = 0;
struct mount *prev_dest_mnt = dest_mnt;
@@ -237,6 +239,10 @@ int propagate_mnt(struct mount *dest_mnt, struct dentry *dest_dentry,
source = get_source(m, prev_dest_mnt, prev_src_mnt, &type);
+ /* Notice when we are propagating across user namespaces */
+ if (m->mnt_ns->user_ns != user_ns)
+ type |= CL_UNPRIVILEGED;
+
child = copy_tree(source, source->mnt.mnt_root, type);
if (IS_ERR(child)) {
ret = PTR_ERR(child);