From: "Eric W. Biederman" <ebiederm@xmission.com>
To: <linux-fsdevel@vger.kernel.org>
Cc: Linux Containers <containers@lists.linux-foundation.org>,
<linux-kernel@vger.kernel.org>, Al Viro <viro@ZenIV.linux.org.uk>,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: [PATCH review 4/6] vfs: Only support slave subtrees across different user namespaces
Date: Mon, 19 Nov 2012 02:50:20 -0800 [thread overview]
Message-ID: <1353322222-27060-4-git-send-email-ebiederm@xmission.com> (raw)
In-Reply-To: <1353322222-27060-1-git-send-email-ebiederm@xmission.com>
From: "Eric W. Biederman" <ebiederm@xmission.com>
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>
---
fs/namespace.c | 11 ++++++++---
fs/pnode.h | 1 +
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 207c7ba..4dfcaf0 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 65c6097..19b853a3 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)
{
--
1.7.5.4
next prev parent reply other threads:[~2012-11-19 10:51 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-19 10:48 [PATCH review 0/6] mount namespace container enhancements Eric W. Biederman
2012-11-19 10:50 ` [PATCH review 1/6] vfs: Allow chroot if you have CAP_SYS_CHROOT in your user namespace Eric W. Biederman
2012-11-19 10:50 ` [PATCH review 2/6] vfs: Add setns support for the mount namespace Eric W. Biederman
2012-11-19 10:50 ` [PATCH review 3/6] vfs: Add a user namespace reference from struct mnt_namespace Eric W. Biederman
2012-11-19 10:50 ` Eric W. Biederman [this message]
2012-11-19 10:50 ` [PATCH review 5/6] vfs: Allow unprivileged manipulation of the mount namespace Eric W. Biederman
2012-11-19 10:50 ` [PATCH review 6/6] userns: fix return value on mntns_install() failure Eric W. Biederman
2012-11-20 3:19 ` [PATCH review 0/6] mount namespace container enhancements Gao feng
2012-11-20 4:29 ` Eric W. Biederman
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