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authorEric W. Biederman <ebiederm@xmission.com>2012-07-31 13:13:04 -0700
committerEric W. Biederman <ebiederm@xmission.com>2012-11-19 05:59:20 -0800
commit7a472ef4be8387bc05a42e16309b02c8ca943a40 (patch)
treed08fef7f89da670c24116805dbe1bcf60e094497
parent771b1371686e0a63e938ada28de020b9a0040f55 (diff)
vfs: Only support slave subtrees across different user namespaces
Sharing mount subtress with mount namespaces created by unprivileged users allows unprivileged mounts created by unprivileged users to propagate to mount namespaces controlled by privileged users. Prevent nasty consequences by changing shared subtrees to slave subtress when an unprivileged users creates a new mount namespace. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
-rw-r--r--fs/namespace.c11
-rw-r--r--fs/pnode.h1
2 files changed, 9 insertions, 3 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 207c7ba84ad..4dfcaf05d17 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -786,7 +786,7 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
if (!mnt)
return ERR_PTR(-ENOMEM);
- if (flag & (CL_SLAVE | CL_PRIVATE))
+ if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
mnt->mnt_group_id = 0; /* not a peer of original */
else
mnt->mnt_group_id = old->mnt_group_id;
@@ -807,7 +807,8 @@ static struct mount *clone_mnt(struct mount *old, struct dentry *root,
list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
br_write_unlock(&vfsmount_lock);
- if (flag & CL_SLAVE) {
+ if ((flag & CL_SLAVE) ||
+ ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
list_add(&mnt->mnt_slave, &old->mnt_slave_list);
mnt->mnt_master = old;
CLEAR_MNT_SHARED(mnt);
@@ -2331,6 +2332,7 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
struct mount *p, *q;
struct mount *old = mnt_ns->root;
struct mount *new;
+ int copy_flags;
new_ns = alloc_mnt_ns(user_ns);
if (IS_ERR(new_ns))
@@ -2338,7 +2340,10 @@ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
down_write(&namespace_sem);
/* First pass: copy the tree topology */
- new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE);
+ copy_flags = CL_COPY_ALL | CL_EXPIRE;
+ if (user_ns != mnt_ns->user_ns)
+ copy_flags |= CL_SHARED_TO_SLAVE;
+ new = copy_tree(old, old->mnt.mnt_root, copy_flags);
if (IS_ERR(new)) {
up_write(&namespace_sem);
free_mnt_ns(new_ns);
diff --git a/fs/pnode.h b/fs/pnode.h
index 65c60979d54..19b853a3445 100644
--- a/fs/pnode.h
+++ b/fs/pnode.h
@@ -22,6 +22,7 @@
#define CL_COPY_ALL 0x04
#define CL_MAKE_SHARED 0x08
#define CL_PRIVATE 0x10
+#define CL_SHARED_TO_SLAVE 0x20
static inline void set_mnt_shared(struct mount *mnt)
{