ns: proc files for namespace naming policy.
Create files under /proc/<pid>/ns/ to allow controlling the
namespaces of a process.
This addresses three specific problems that can make namespaces hard to
work with.
- Namespaces require a dedicated process to pin them in memory.
- It is not possible to use a namespace unless you are the child
of the original creator.
- Namespaces don't have names that userspace can use to talk about
them.
The namespace files under /proc/<pid>/ns/ can be opened and the
file descriptor can be used to talk about a specific namespace, and
to keep the specified namespace alive.
A namespace can be kept alive by either holding the file descriptor
open or bind mounting the file someplace else. aka:
mount --bind /proc/self/ns/net /some/filesystem/path
mount --bind /proc/self/fd/<N> /some/filesystem/path
This allows namespaces to be named with userspace policy.
It requires additional support to make use of these filedescriptors
and that will be comming in the following patches.
Acked-by: Daniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
new file mode 100644
index 0000000..6ae9f07
--- /dev/null
+++ b/fs/proc/namespaces.c
@@ -0,0 +1,188 @@
+#include <linux/proc_fs.h>
+#include <linux/nsproxy.h>
+#include <linux/sched.h>
+#include <linux/ptrace.h>
+#include <linux/fs_struct.h>
+#include <linux/mount.h>
+#include <linux/path.h>
+#include <linux/namei.h>
+#include <linux/file.h>
+#include <linux/utsname.h>
+#include <net/net_namespace.h>
+#include <linux/mnt_namespace.h>
+#include <linux/ipc_namespace.h>
+#include <linux/pid_namespace.h>
+#include "internal.h"
+
+
+static const struct proc_ns_operations *ns_entries[] = {
+};
+
+static const struct file_operations ns_file_operations = {
+ .llseek = no_llseek,
+};
+
+static struct dentry *proc_ns_instantiate(struct inode *dir,
+ struct dentry *dentry, struct task_struct *task, const void *ptr)
+{
+ const struct proc_ns_operations *ns_ops = ptr;
+ struct inode *inode;
+ struct proc_inode *ei;
+ struct dentry *error = ERR_PTR(-ENOENT);
+
+ inode = proc_pid_make_inode(dir->i_sb, task);
+ if (!inode)
+ goto out;
+
+ ei = PROC_I(inode);
+ inode->i_mode = S_IFREG|S_IRUSR;
+ inode->i_fop = &ns_file_operations;
+ ei->ns_ops = ns_ops;
+ ei->ns = ns_ops->get(task);
+ if (!ei->ns)
+ goto out_iput;
+
+ dentry->d_op = &pid_dentry_operations;
+ d_add(dentry, inode);
+ /* Close the race of the process dying before we return the dentry */
+ if (pid_revalidate(dentry, NULL))
+ error = NULL;
+out:
+ return error;
+out_iput:
+ iput(inode);
+ goto out;
+}
+
+static int proc_ns_fill_cache(struct file *filp, void *dirent,
+ filldir_t filldir, struct task_struct *task,
+ const struct proc_ns_operations *ops)
+{
+ return proc_fill_cache(filp, dirent, filldir,
+ ops->name, strlen(ops->name),
+ proc_ns_instantiate, task, ops);
+}
+
+static int proc_ns_dir_readdir(struct file *filp, void *dirent,
+ filldir_t filldir)
+{
+ int i;
+ struct dentry *dentry = filp->f_path.dentry;
+ struct inode *inode = dentry->d_inode;
+ struct task_struct *task = get_proc_task(inode);
+ const struct proc_ns_operations **entry, **last;
+ ino_t ino;
+ int ret;
+
+ ret = -ENOENT;
+ if (!task)
+ goto out_no_task;
+
+ ret = -EPERM;
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ goto out;
+
+ ret = 0;
+ i = filp->f_pos;
+ switch (i) {
+ case 0:
+ ino = inode->i_ino;
+ if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
+ goto out;
+ i++;
+ filp->f_pos++;
+ /* fall through */
+ case 1:
+ ino = parent_ino(dentry);
+ if (filldir(dirent, "..", 2, i, ino, DT_DIR) < 0)
+ goto out;
+ i++;
+ filp->f_pos++;
+ /* fall through */
+ default:
+ i -= 2;
+ if (i >= ARRAY_SIZE(ns_entries)) {
+ ret = 1;
+ goto out;
+ }
+ entry = ns_entries + i;
+ last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
+ while (entry <= last) {
+ if (proc_ns_fill_cache(filp, dirent, filldir,
+ task, *entry) < 0)
+ goto out;
+ filp->f_pos++;
+ entry++;
+ }
+ }
+
+ ret = 1;
+out:
+ put_task_struct(task);
+out_no_task:
+ return ret;
+}
+
+const struct file_operations proc_ns_dir_operations = {
+ .read = generic_read_dir,
+ .readdir = proc_ns_dir_readdir,
+};
+
+static struct dentry *proc_ns_dir_lookup(struct inode *dir,
+ struct dentry *dentry, struct nameidata *nd)
+{
+ struct dentry *error;
+ struct task_struct *task = get_proc_task(dir);
+ const struct proc_ns_operations **entry, **last;
+ unsigned int len = dentry->d_name.len;
+
+ error = ERR_PTR(-ENOENT);
+
+ if (!task)
+ goto out_no_task;
+
+ error = ERR_PTR(-EPERM);
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ goto out;
+
+ last = &ns_entries[ARRAY_SIZE(ns_entries) - 1];
+ for (entry = ns_entries; entry <= last; entry++) {
+ if (strlen((*entry)->name) != len)
+ continue;
+ if (!memcmp(dentry->d_name.name, (*entry)->name, len))
+ break;
+ }
+ if (entry > last)
+ goto out;
+
+ error = proc_ns_instantiate(dir, dentry, task, *entry);
+out:
+ put_task_struct(task);
+out_no_task:
+ return error;
+}
+
+const struct inode_operations proc_ns_dir_inode_operations = {
+ .lookup = proc_ns_dir_lookup,
+ .getattr = pid_getattr,
+ .setattr = proc_setattr,
+};
+
+struct file *proc_ns_fget(int fd)
+{
+ struct file *file;
+
+ file = fget(fd);
+ if (!file)
+ return ERR_PTR(-EBADF);
+
+ if (file->f_op != &ns_file_operations)
+ goto out_invalid;
+
+ return file;
+
+out_invalid:
+ fput(file);
+ return ERR_PTR(-EINVAL);
+}
+