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    Subject[PATCH 1/7] ns: proc files for namespace naming policy.
    Date
    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.

    Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    ---
    fs/proc/Makefile | 1 +
    fs/proc/base.c | 20 ++---
    fs/proc/inode.c | 7 ++
    fs/proc/internal.h | 18 +++++
    fs/proc/namespaces.c | 188 +++++++++++++++++++++++++++++++++++++++++++++++
    include/linux/proc_fs.h | 18 +++++
    6 files changed, 241 insertions(+), 11 deletions(-)
    create mode 100644 fs/proc/namespaces.c

    diff --git a/fs/proc/Makefile b/fs/proc/Makefile
    index df434c5..c1c7293 100644
    --- a/fs/proc/Makefile
    +++ b/fs/proc/Makefile
    @@ -20,6 +20,7 @@ proc-y += stat.o
    proc-y += uptime.o
    proc-y += version.o
    proc-y += softirqs.o
    +proc-y += namespaces.o
    proc-$(CONFIG_PROC_SYSCTL) += proc_sysctl.o
    proc-$(CONFIG_NET) += proc_net.o
    proc-$(CONFIG_PROC_KCORE) += kcore.o
    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index dfa5327..dc8bca7 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -600,7 +600,7 @@ static int proc_fd_access_allowed(struct inode *inode)
    return allowed;
    }

    -static int proc_setattr(struct dentry *dentry, struct iattr *attr)
    +int proc_setattr(struct dentry *dentry, struct iattr *attr)
    {
    int error;
    struct inode *inode = dentry->d_inode;
    @@ -1736,8 +1736,7 @@ static int task_dumpable(struct task_struct *task)
    return 0;
    }

    -
    -static struct inode *proc_pid_make_inode(struct super_block * sb, struct task_struct *task)
    +struct inode *proc_pid_make_inode(struct super_block * sb, struct task_struct *task)
    {
    struct inode * inode;
    struct proc_inode *ei;
    @@ -1779,7 +1778,7 @@ out_unlock:
    return NULL;
    }

    -static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
    +int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
    {
    struct inode *inode = dentry->d_inode;
    struct task_struct *task;
    @@ -1820,7 +1819,7 @@ static int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat
    * made this apply to all per process world readable and executable
    * directories.
    */
    -static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
    +int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
    {
    struct inode *inode;
    struct task_struct *task;
    @@ -1862,7 +1861,7 @@ static int pid_delete_dentry(const struct dentry * dentry)
    return !proc_pid(dentry->d_inode)->tasks[PIDTYPE_PID].first;
    }

    -static const struct dentry_operations pid_dentry_operations =
    +const struct dentry_operations pid_dentry_operations =
    {
    .d_revalidate = pid_revalidate,
    .d_delete = pid_delete_dentry,
    @@ -1870,9 +1869,6 @@ static const struct dentry_operations pid_dentry_operations =

    /* Lookups */

    -typedef struct dentry *instantiate_t(struct inode *, struct dentry *,
    - struct task_struct *, const void *);
    -
    /*
    * Fill a directory entry.
    *
    @@ -1885,8 +1881,8 @@ typedef struct dentry *instantiate_t(struct inode *, struct dentry *,
    * reported by readdir in sync with the inode numbers reported
    * by stat.
    */
    -static int proc_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    - char *name, int len,
    +int proc_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    + const char *name, int len,
    instantiate_t instantiate, struct task_struct *task, const void *ptr)
    {
    struct dentry *child, *dir = filp->f_path.dentry;
    @@ -2820,6 +2816,7 @@ static const struct pid_entry tgid_base_stuff[] = {
    DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
    DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
    DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
    + DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
    #ifdef CONFIG_NET
    DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
    #endif
    @@ -3168,6 +3165,7 @@ out_no_task:
    static const struct pid_entry tid_base_stuff[] = {
    DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
    DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations),
    + DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
    REG("environ", S_IRUSR, proc_environ_operations),
    INF("auxv", S_IRUSR, proc_pid_auxv),
    ONE("status", S_IRUGO, proc_pid_status),
    diff --git a/fs/proc/inode.c b/fs/proc/inode.c
    index d15aa1b..74b48cf 100644
    --- a/fs/proc/inode.c
    +++ b/fs/proc/inode.c
    @@ -28,6 +28,7 @@ static void proc_evict_inode(struct inode *inode)
    {
    struct proc_dir_entry *de;
    struct ctl_table_header *head;
    + const struct proc_ns_operations *ns_ops;

    truncate_inode_pages(&inode->i_data, 0);
    end_writeback(inode);
    @@ -44,6 +45,10 @@ static void proc_evict_inode(struct inode *inode)
    rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
    sysctl_head_put(head);
    }
    + /* Release any associated namespace */
    + ns_ops = PROC_I(inode)->ns_ops;
    + if (ns_ops && ns_ops->put)
    + ns_ops->put(PROC_I(inode)->ns);
    }

    static struct kmem_cache * proc_inode_cachep;
    @@ -62,6 +67,8 @@ static struct inode *proc_alloc_inode(struct super_block *sb)
    ei->pde = NULL;
    ei->sysctl = NULL;
    ei->sysctl_entry = NULL;
    + ei->ns = NULL;
    + ei->ns_ops = NULL;
    inode = &ei->vfs_inode;
    inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
    return inode;
    diff --git a/fs/proc/internal.h b/fs/proc/internal.h
    index c03e8d3..96245a1 100644
    --- a/fs/proc/internal.h
    +++ b/fs/proc/internal.h
    @@ -119,3 +119,21 @@ struct inode *proc_get_inode(struct super_block *, struct proc_dir_entry *);
    */
    int proc_readdir(struct file *, void *, filldir_t);
    struct dentry *proc_lookup(struct inode *, struct dentry *, struct nameidata *);
    +
    +
    +
    +/* Lookups */
    +typedef struct dentry *instantiate_t(struct inode *, struct dentry *,
    + struct task_struct *, const void *);
    +int proc_fill_cache(struct file *filp, void *dirent, filldir_t filldir,
    + const char *name, int len,
    + instantiate_t instantiate, struct task_struct *task, const void *ptr);
    +int pid_revalidate(struct dentry *dentry, struct nameidata *nd);
    +struct inode *proc_pid_make_inode(struct super_block * sb, struct task_struct *task);
    +extern const struct dentry_operations pid_dentry_operations;
    +int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
    +int proc_setattr(struct dentry *dentry, struct iattr *attr);
    +
    +extern const struct inode_operations proc_ns_dir_inode_operations;
    +extern const struct file_operations proc_ns_dir_operations;
    +
    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);
    +}
    +
    diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
    index 838c114..a6d2c6d 100644
    --- a/include/linux/proc_fs.h
    +++ b/include/linux/proc_fs.h
    @@ -179,6 +179,8 @@ extern void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file);
    extern struct file *get_mm_exe_file(struct mm_struct *mm);
    extern void dup_mm_exe_file(struct mm_struct *oldmm, struct mm_struct *newmm);

    +extern struct file *proc_ns_fget(int fd);
    +
    #else

    #define proc_net_fops_create(net, name, mode, fops) ({ (void)(mode), NULL; })
    @@ -239,6 +241,11 @@ static inline void dup_mm_exe_file(struct mm_struct *oldmm,
    struct mm_struct *newmm)
    {}

    +static inline struct file *proc_ns_fget(int fd)
    +{
    + return ERR_PTR(-EINVAL);
    +}
    +
    #endif /* CONFIG_PROC_FS */

    #if !defined(CONFIG_PROC_KCORE)
    @@ -250,6 +257,15 @@ kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
    extern void kclist_add(struct kcore_list *, void *, size_t, int type);
    #endif

    +struct nsproxy;
    +struct proc_ns_operations {
    + const char *name;
    + int type;
    + void *(*get)(struct task_struct *task);
    + void (*put)(void *ns);
    + int (*install)(struct nsproxy *nsproxy, void *ns);
    +};
    +
    union proc_op {
    int (*proc_get_link)(struct inode *, struct path *);
    int (*proc_read)(struct task_struct *task, char *page);
    @@ -268,6 +284,8 @@ struct proc_inode {
    struct proc_dir_entry *pde;
    struct ctl_table_header *sysctl;
    struct ctl_table *sysctl_entry;
    + void *ns;
    + const struct proc_ns_operations *ns_ops;
    struct inode vfs_inode;
    };

    --
    1.6.5.2.143.g8cc62


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