Commit e149ed2b authored by Al Viro's avatar Al Viro

take the targets of /proc/*/ns/* symlinks to separate fs

New pseudo-filesystem: nsfs.  Targets of /proc/*/ns/* live there now.
It's not mountable (not even registered, so it's not in /proc/filesystems,
etc.).  Files on it *are* bindable - we explicitly permit that in do_loopback().

This stuff lives in fs/nsfs.c now; proc_ns_fget() moved there as well.
get_proc_ns() is a macro now (it's simply returning ->i_private; would
have been an inline, if not for header ordering headache).
proc_ns_inode() is an ex-parrot.  The interface used in procfs is
ns_get_path(path, task, ops) and ns_get_name(buf, size, task, ops).

Dentries and inodes are never hashed; a non-counting reference to dentry
is stashed in ns_common (removed by ->d_prune()) and reused by ns_get_path()
if present.  See ns_get_path()/ns_prune_dentry/nsfs_evict() for details
of that mechanism.

As the result, proc_ns_follow_link() has stopped poking in nd->path.mnt;
it does nd_jump_link() on a consistent <vfsmount,dentry> pair it gets
from ns_get_path().
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent f77c8014
......@@ -11,7 +11,7 @@ obj-y := open.o read_write.o file_table.o super.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o \
stack.o fs_struct.o statfs.o fs_pin.o
stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
......
......@@ -147,3 +147,8 @@ extern const struct file_operations pipefifo_fops;
*/
extern void sb_pin_kill(struct super_block *sb);
extern void mnt_pin_kill(struct mount *m);
/*
* fs/nsfs.c
*/
extern struct dentry_operations ns_dentry_operations;
......@@ -1569,8 +1569,8 @@ SYSCALL_DEFINE1(oldumount, char __user *, name)
static bool is_mnt_ns_file(struct dentry *dentry)
{
/* Is this a proxy for a mount namespace? */
struct inode *inode = dentry->d_inode;
return proc_ns_inode(inode) && dentry->d_fsdata == &mntns_operations;
return dentry->d_op == &ns_dentry_operations &&
dentry->d_fsdata == &mntns_operations;
}
struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
......@@ -2016,7 +2016,10 @@ static int do_loopback(struct path *path, const char *old_name,
if (IS_MNT_UNBINDABLE(old))
goto out2;
if (!check_mnt(parent) || !check_mnt(old))
if (!check_mnt(parent))
goto out2;
if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations)
goto out2;
if (!recurse && has_locked_children(old, old_path.dentry))
......
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/proc_ns.h>
#include <linux/magic.h>
#include <linux/ktime.h>
static struct vfsmount *nsfs_mnt;
static const struct file_operations ns_file_operations = {
.llseek = no_llseek,
};
static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
{
struct inode *inode = dentry->d_inode;
const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
ns_ops->name, inode->i_ino);
}
static void ns_prune_dentry(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
if (inode) {
struct ns_common *ns = inode->i_private;
atomic_long_set(&ns->stashed, 0);
}
}
const struct dentry_operations ns_dentry_operations =
{
.d_prune = ns_prune_dentry,
.d_delete = always_delete_dentry,
.d_dname = ns_dname,
};
static void nsfs_evict(struct inode *inode)
{
struct ns_common *ns = inode->i_private;
clear_inode(inode);
ns->ops->put(ns);
}
void *ns_get_path(struct path *path, struct task_struct *task,
const struct proc_ns_operations *ns_ops)
{
struct vfsmount *mnt = mntget(nsfs_mnt);
struct qstr qname = { .name = "", };
struct dentry *dentry;
struct inode *inode;
struct ns_common *ns;
unsigned long d;
again:
ns = ns_ops->get(task);
if (!ns) {
mntput(mnt);
return ERR_PTR(-ENOENT);
}
rcu_read_lock();
d = atomic_long_read(&ns->stashed);
if (!d)
goto slow;
dentry = (struct dentry *)d;
if (!lockref_get_not_dead(&dentry->d_lockref))
goto slow;
rcu_read_unlock();
ns_ops->put(ns);
got_it:
path->mnt = mnt;
path->dentry = dentry;
return NULL;
slow:
rcu_read_unlock();
inode = new_inode_pseudo(mnt->mnt_sb);
if (!inode) {
ns_ops->put(ns);
mntput(mnt);
return ERR_PTR(-ENOMEM);
}
inode->i_ino = ns->inum;
inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
inode->i_flags |= S_IMMUTABLE;
inode->i_mode = S_IFREG | S_IRUGO;
inode->i_fop = &ns_file_operations;
inode->i_private = ns;
dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
if (!dentry) {
iput(inode);
mntput(mnt);
return ERR_PTR(-ENOMEM);
}
d_instantiate(dentry, inode);
dentry->d_fsdata = (void *)ns_ops;
d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
if (d) {
d_delete(dentry); /* make sure ->d_prune() does nothing */
dput(dentry);
cpu_relax();
goto again;
}
goto got_it;
}
int ns_get_name(char *buf, size_t size, struct task_struct *task,
const struct proc_ns_operations *ns_ops)
{
struct ns_common *ns;
int res = -ENOENT;
ns = ns_ops->get(task);
if (ns) {
res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
ns_ops->put(ns);
}
return res;
}
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);
}
static const struct super_operations nsfs_ops = {
.statfs = simple_statfs,
.evict_inode = nsfs_evict,
};
static struct dentry *nsfs_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
&ns_dentry_operations, NSFS_MAGIC);
}
static struct file_system_type nsfs = {
.name = "nsfs",
.mount = nsfs_mount,
.kill_sb = kill_anon_super,
};
void __init nsfs_init(void)
{
nsfs_mnt = kern_mount(&nsfs);
if (IS_ERR(nsfs_mnt))
panic("can't set nsfs up\n");
nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
}
......@@ -32,7 +32,6 @@ static void proc_evict_inode(struct inode *inode)
{
struct proc_dir_entry *de;
struct ctl_table_header *head;
struct ns_common *ns;
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
......@@ -49,10 +48,6 @@ static void proc_evict_inode(struct inode *inode)
RCU_INIT_POINTER(PROC_I(inode)->sysctl, NULL);
sysctl_head_put(head);
}
/* Release any associated namespace */
ns = PROC_I(inode)->ns.ns;
if (ns && ns->ops)
ns->ops->put(ns);
}
static struct kmem_cache * proc_inode_cachep;
......
#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>
......@@ -34,139 +30,45 @@ static const struct proc_ns_operations *ns_entries[] = {
&mntns_operations,
};
static const struct file_operations ns_file_operations = {
.llseek = no_llseek,
};
static const struct inode_operations ns_inode_operations = {
.setattr = proc_setattr,
};
static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
{
struct inode *inode = dentry->d_inode;
const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
ns_ops->name, inode->i_ino);
}
const struct dentry_operations ns_dentry_operations =
{
.d_delete = always_delete_dentry,
.d_dname = ns_dname,
};
static struct dentry *proc_ns_get_dentry(struct super_block *sb,
struct task_struct *task, const struct proc_ns_operations *ns_ops)
{
struct dentry *dentry, *result;
struct inode *inode;
struct proc_inode *ei;
struct qstr qname = { .name = "", };
struct ns_common *ns;
ns = ns_ops->get(task);
if (!ns)
return ERR_PTR(-ENOENT);
dentry = d_alloc_pseudo(sb, &qname);
if (!dentry) {
ns_ops->put(ns);
return ERR_PTR(-ENOMEM);
}
dentry->d_fsdata = (void *)ns_ops;
inode = iget_locked(sb, ns->inum);
if (!inode) {
dput(dentry);
ns_ops->put(ns);
return ERR_PTR(-ENOMEM);
}
ei = PROC_I(inode);
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.ns_ops = ns_ops;
ei->ns.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);
if (result) {
dput(dentry);
dentry = result;
}
return dentry;
}
static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd)
{
struct inode *inode = dentry->d_inode;
struct super_block *sb = inode->i_sb;
struct proc_inode *ei = PROC_I(inode);
const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns.ns_ops;
struct task_struct *task;
struct path ns_path;
void *error = ERR_PTR(-EACCES);
task = get_proc_task(inode);
if (!task)
goto out;
if (!ptrace_may_access(task, PTRACE_MODE_READ))
goto out_put_task;
ns_path.dentry = proc_ns_get_dentry(sb, task, ei->ns.ns_ops);
if (IS_ERR(ns_path.dentry)) {
error = ERR_CAST(ns_path.dentry);
goto out_put_task;
}
return error;
ns_path.mnt = mntget(nd->path.mnt);
if (ptrace_may_access(task, PTRACE_MODE_READ)) {
error = ns_get_path(&ns_path, task, ns_ops);
if (!error)
nd_jump_link(nd, &ns_path);
error = NULL;
out_put_task:
}
put_task_struct(task);
out:
return error;
}
static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int buflen)
{
struct inode *inode = dentry->d_inode;
struct proc_inode *ei = PROC_I(inode);
const struct proc_ns_operations *ns_ops = ei->ns.ns_ops;
const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns.ns_ops;
struct task_struct *task;
struct ns_common *ns;
char name[50];
int res = -EACCES;
task = get_proc_task(inode);
if (!task)
goto out;
if (!ptrace_may_access(task, PTRACE_MODE_READ))
goto out_put_task;
res = -ENOENT;
ns = ns_ops->get(task);
if (!ns)
goto out_put_task;
return res;
snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns->inum);
if (ptrace_may_access(task, PTRACE_MODE_READ)) {
res = ns_get_name(name, sizeof(name), task, ns_ops);
if (res >= 0)
res = readlink_copy(buffer, buflen, name);
ns_ops->put(ns);
out_put_task:
}
put_task_struct(task);
out:
return res;
}
......@@ -268,31 +170,3 @@ const struct inode_operations proc_ns_dir_inode_operations = {
.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);
}
struct ns_common *get_proc_ns(struct inode *inode)
{
return PROC_I(inode)->ns.ns;
}
bool proc_ns_inode(struct inode *inode)
{
return inode->i_fop == &ns_file_operations;
}
......@@ -4,6 +4,7 @@
struct proc_ns_operations;
struct ns_common {
atomic_long_t stashed;
const struct proc_ns_operations *ops;
unsigned int inum;
};
......
......@@ -4,9 +4,11 @@
#ifndef _LINUX_PROC_NS_H
#define _LINUX_PROC_NS_H
#include <linux/ns_common.h>
struct pid_namespace;
struct nsproxy;
struct ns_common;
struct path;
struct proc_ns_operations {
const char *name;
......@@ -38,35 +40,38 @@ enum {
extern int pid_ns_prepare_proc(struct pid_namespace *ns);
extern void pid_ns_release_proc(struct pid_namespace *ns);
extern struct file *proc_ns_fget(int fd);
extern struct ns_common *get_proc_ns(struct inode *);
extern int proc_alloc_inum(unsigned int *pino);
extern void proc_free_inum(unsigned int inum);
extern bool proc_ns_inode(struct inode *inode);
#else /* CONFIG_PROC_FS */
static inline int pid_ns_prepare_proc(struct pid_namespace *ns) { return 0; }
static inline void pid_ns_release_proc(struct pid_namespace *ns) {}
static inline struct file *proc_ns_fget(int fd)
{
return ERR_PTR(-EINVAL);
}
static inline struct ns_common *get_proc_ns(struct inode *inode) { return NULL; }
static inline int proc_alloc_inum(unsigned int *inum)
{
*inum = 1;
return 0;
}
static inline void proc_free_inum(unsigned int inum) {}
static inline bool proc_ns_inode(struct inode *inode) { return false; }
#endif /* CONFIG_PROC_FS */
#define ns_alloc_inum(ns) proc_alloc_inum(&(ns)->inum)
static inline int ns_alloc_inum(struct ns_common *ns)
{
atomic_long_set(&ns->stashed, 0);
return proc_alloc_inum(&ns->inum);
}
#define ns_free_inum(ns) proc_free_inum((ns)->inum)
extern struct file *proc_ns_fget(int fd);
#define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
extern void *ns_get_path(struct path *path, struct task_struct *task,
const struct proc_ns_operations *ns_ops);
extern int ns_get_name(char *buf, size_t size, struct task_struct *task,
const struct proc_ns_operations *ns_ops);
extern void nsfs_init(void);
#endif /* _LINUX_PROC_NS_H */
......@@ -72,5 +72,6 @@
#define MTD_INODE_FS_MAGIC 0x11307854
#define ANON_INODE_FS_MAGIC 0x09041934
#define BTRFS_TEST_MAGIC 0x73727279
#define NSFS_MAGIC 0x6e736673
#endif /* __LINUX_MAGIC_H__ */
......@@ -78,6 +78,7 @@
#include <linux/context_tracking.h>
#include <linux/random.h>
#include <linux/list.h>
#include <linux/proc_ns.h>
#include <asm/io.h>
#include <asm/bugs.h>
......@@ -660,6 +661,7 @@ asmlinkage __visible void __init start_kernel(void)
/* rootfs populating might need page-writeback */
page_writeback_init();
proc_root_init();
nsfs_init();
cgroup_init();
cpuset_init();
taskstats_init_early();
......
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