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

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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: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2014-11-01 10:57:28 -04:00
parent f77c80142e
commit e149ed2b80
10 changed files with 208 additions and 161 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/proc/namespaces.c
+13 -139
View File
@@ -1,10 +1,6 @@
#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;
return error;
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;
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);
}
ns_path.mnt = mntget(nd->path.mnt);
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;
return res;
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;
snprintf(name, sizeof(name), "%s:[%u]", ns_ops->name, ns->inum);
res = readlink_copy(buffer, buflen, name);
ns_ops->put(ns);
out_put_task:
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);
}
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;
}