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authorEric W. Biederman <ebiederm@xmission.com>2011-06-15 10:21:48 -0700
committerEric W. Biederman <ebiederm@xmission.com>2012-11-20 04:19:49 -0800
commit98f842e675f96ffac96e6c50315790912b2812be (patch)
treeed4dee9a6e54e3443e9f3f1614c8a2fcf9b31e0a /fs
parentbf056bfa80596a5d14b26b17276a56a0dcb080e5 (diff)
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proc: Usable inode numbers for the namespace file descriptors.
Assign a unique proc inode to each namespace, and use that inode number to ensure we only allocate at most one proc inode for every namespace in proc. A single proc inode per namespace allows userspace to test to see if two processes are in the same namespace. This has been a long requested feature and only blocked because a naive implementation would put the id in a global space and would ultimately require having a namespace for the names of namespaces, making migration and certain virtualization tricks impossible. We still don't have per superblock inode numbers for proc, which appears necessary for application unaware checkpoint/restart and migrations (if the application is using namespace file descriptors) but that is now allowd by the design if it becomes important. I have preallocated the ipc and uts initial proc inode numbers so their structures can be statically initialized. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/mount.h1
-rw-r--r--fs/namespace.c14
-rw-r--r--fs/proc/namespaces.c24
3 files changed, 29 insertions, 10 deletions
diff --git a/fs/mount.h b/fs/mount.h
index 630fafc616bb..cd5007980400 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -4,6 +4,7 @@
struct mnt_namespace {
atomic_t count;
+ unsigned int proc_inum;
struct mount * root;
struct list_head list;
struct user_namespace *user_ns;
diff --git a/fs/namespace.c b/fs/namespace.c
index cab78a74aca3..c1bbe86f4920 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2301,6 +2301,7 @@ dput_out:
static void free_mnt_ns(struct mnt_namespace *ns)
{
+ proc_free_inum(ns->proc_inum);
put_user_ns(ns->user_ns);
kfree(ns);
}
@@ -2317,10 +2318,16 @@ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
{
struct mnt_namespace *new_ns;
+ int ret;
new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
if (!new_ns)
return ERR_PTR(-ENOMEM);
+ ret = proc_alloc_inum(&new_ns->proc_inum);
+ if (ret) {
+ kfree(new_ns);
+ return ERR_PTR(ret);
+ }
new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
atomic_set(&new_ns->count, 1);
new_ns->root = NULL;
@@ -2799,10 +2806,17 @@ static int mntns_install(struct nsproxy *nsproxy, void *ns)
return 0;
}
+static unsigned int mntns_inum(void *ns)
+{
+ struct mnt_namespace *mnt_ns = ns;
+ return mnt_ns->proc_inum;
+}
+
const struct proc_ns_operations mntns_operations = {
.name = "mnt",
.type = CLONE_NEWNS,
.get = mntns_get,
.put = mntns_put,
.install = mntns_install,
+ .inum = mntns_inum,
};
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 7a6d8d69cdb8..b7a47196c8c3 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -82,7 +82,7 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
return ERR_PTR(-ENOMEM);
}
- inode = new_inode(sb);
+ inode = iget_locked(sb, ns_ops->inum(ns));
if (!inode) {
dput(dentry);
ns_ops->put(ns);
@@ -90,13 +90,17 @@ static struct dentry *proc_ns_get_dentry(struct super_block *sb,
}
ei = PROC_I(inode);
- inode->i_ino = get_next_ino();
- inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
- inode->i_op = &ns_inode_operations;
- inode->i_mode = S_IFREG | S_IRUGO;
- inode->i_fop = &ns_file_operations;
- ei->ns_ops = ns_ops;
- ei->ns = ns;
+ if (inode->i_state & I_NEW) {
+ inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
+ inode->i_op = &ns_inode_operations;
+ inode->i_mode = S_IFREG | S_IRUGO;
+ inode->i_fop = &ns_file_operations;
+ ei->ns_ops = ns_ops;
+ ei->ns = ns;
+ unlock_new_inode(inode);
+ } else {
+ ns_ops->put(ns);
+ }
d_set_d_op(dentry, &ns_dentry_operations);
result = d_instantiate_unique(dentry, inode);
@@ -162,12 +166,12 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
if (!ns)
goto out_put_task;
- snprintf(name, sizeof(name), "%s", ns_ops->name);
+ snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns_ops->inum(ns));
len = strlen(name);
if (len > buflen)
len = buflen;
- if (copy_to_user(buffer, ns_ops->name, len))
+ if (copy_to_user(buffer, name, len))
len = -EFAULT;
ns_ops->put(ns);