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[NET]: Make /proc/net a symlink on /proc/self/net (v3) 

Current /proc/net is done with so called "shadows", but current
implementation is broken and has little chances to get fixed.

The problem is that dentries subtree of /proc/net directory has
fancy revalidation rules to make processes living in different
net namespaces see different entries in /proc/net subtree, but
currently, tasks see in the /proc/net subdir the contents of any
other namespace, depending on who opened the file first.

The proposed fix is to turn /proc/net into a symlink, which points
to /proc/self/net, which in turn shows what previously was in
/proc/net - the network-related info, from the net namespace the
appropriate task lives in.

# ls -l /proc/net
lrwxrwxrwx  1 root root 8 Mar  5 15:17 /proc/net -> self/net

In other words - this behaves like /proc/mounts, but unlike
"mounts", "net" is not a file, but a directory.

Changes from v2:
* Fixed discrepancy of /proc/net nlink count and selinux labeling
  screwup pointed out by Stephen.

  To get the correct nlink count the ->getattr callback for /proc/net
  is overridden to read one from the net->proc_net entry.

  To make selinux still work the net->proc_net entry is initialized
  properly, i.e. with the "net" name and the proc_net parent.

Selinux fixes are
Acked-by:  Stephen Smalley <sds@tycho.nsa.gov>

Changes from v1:
* Fixed a task_struct leak in get_proc_task_net, pointed out by Paul.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Pavel Emelyanov 2008-03-07 11:08:40 -08:00 committed by David S. Miller
parent 1ff82fe002
commit e9720acd72
6 changed files with 114 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/proc/base.c
View File

@ -2274,6 +2274,7 @@ static const struct pid_entry tgid_base_stuff[] = {
DIR("task", S_IRUGO|S_IXUGO, task),
DIR("fd", S_IRUSR|S_IXUSR, fd),
DIR("fdinfo", S_IRUSR|S_IXUSR, fdinfo),
DIR("net", S_IRUGO|S_IXUSR, net),
REG("environ", S_IRUSR, environ),
INF("auxv", S_IRUSR, pid_auxv),
ONE("status", S_IRUGO, pid_status),

26
fs/proc/generic.c
View File

@ -377,15 +377,14 @@ static struct dentry_operations proc_dentry_operations =
* Don't create negative dentries here, return -ENOENT by hand
* instead.
*/
struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nameidata *nd)
struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
struct dentry *dentry)
{
struct inode *inode = NULL;
struct proc_dir_entry * de;
int error = -ENOENT;
lock_kernel();
spin_lock(&proc_subdir_lock);
de = PDE(dir);
if (de) {
for (de = de->subdir; de ; de = de->next) {
if (de->namelen != dentry->d_name.len)
@ -393,8 +392,6 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
unsigned int ino;
if (de->shadow_proc)
de = de->shadow_proc(current, de);
ino = de->low_ino;
de_get(de);
spin_unlock(&proc_subdir_lock);
@ -417,6 +414,12 @@ out_unlock:
return ERR_PTR(error);
}
struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
return proc_lookup_de(PDE(dir), dir, dentry);
}
/*
* This returns non-zero if at EOF, so that the /proc
* root directory can use this and check if it should
@ -426,10 +429,9 @@ out_unlock:
* value of the readdir() call, as long as it's non-negative
* for success..
*/
int proc_readdir(struct file * filp,
void * dirent, filldir_t filldir)
int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
filldir_t filldir)
{
struct proc_dir_entry * de;
unsigned int ino;
int i;
struct inode *inode = filp->f_path.dentry->d_inode;
@ -438,7 +440,6 @@ int proc_readdir(struct file * filp,
lock_kernel();
ino = inode->i_ino;
de = PDE(inode);
if (!de) {
ret = -EINVAL;
goto out;
@ -499,6 +500,13 @@ out: unlock_kernel();
return ret;
}
int proc_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
struct inode *inode = filp->f_path.dentry->d_inode;
return proc_readdir_de(PDE(inode), filp, dirent, filldir);
}
/*
* These are the generic /proc directory operations. They
* use the in-memory "struct proc_dir_entry" tree to parse

7
fs/proc/internal.h
View File

@ -64,6 +64,8 @@ extern const struct file_operations proc_numa_maps_operations;
extern const struct file_operations proc_smaps_operations;
extern const struct file_operations proc_clear_refs_operations;
extern const struct file_operations proc_pagemap_operations;
extern const struct file_operations proc_net_operations;
extern const struct inode_operations proc_net_inode_operations;
void free_proc_entry(struct proc_dir_entry *de);
@ -83,3 +85,8 @@ static inline int proc_fd(struct inode *inode)
{
return PROC_I(inode)->fd;
}
struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *ino,
struct dentry *dentry);
int proc_readdir_de(struct proc_dir_entry *de, struct file *filp, void *dirent,
filldir_t filldir);

117
fs/proc/proc_net.c
View File

@ -63,6 +63,82 @@ int seq_release_net(struct inode *ino, struct file *f)
}
EXPORT_SYMBOL_GPL(seq_release_net);
static struct net *get_proc_task_net(struct inode *dir)
{
struct task_struct *task;
struct nsproxy *ns;
struct net *net = NULL;
rcu_read_lock();
task = pid_task(proc_pid(dir), PIDTYPE_PID);
if (task != NULL) {
ns = task_nsproxy(task);
if (ns != NULL)
net = get_net(ns->net_ns);
}
rcu_read_unlock();
return net;
}
static struct dentry *proc_tgid_net_lookup(struct inode *dir,
struct dentry *dentry, struct nameidata *nd)
{
struct dentry *de;
struct net *net;
de = ERR_PTR(-ENOENT);
net = get_proc_task_net(dir);
if (net != NULL) {
de = proc_lookup_de(net->proc_net, dir, dentry);
put_net(net);
}
return de;
}
static int proc_tgid_net_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct inode *inode = dentry->d_inode;
struct net *net;
net = get_proc_task_net(inode);
generic_fillattr(inode, stat);
if (net != NULL) {
stat->nlink = net->proc_net->nlink;
put_net(net);
}
return 0;
}
const struct inode_operations proc_net_inode_operations = {
.lookup = proc_tgid_net_lookup,
.getattr = proc_tgid_net_getattr,
};
static int proc_tgid_net_readdir(struct file *filp, void *dirent,
filldir_t filldir)
{
int ret;
struct net *net;
ret = -EINVAL;
net = get_proc_task_net(filp->f_path.dentry->d_inode);
if (net != NULL) {
ret = proc_readdir_de(net->proc_net, filp, dirent, filldir);
put_net(net);
}
return ret;
}
const struct file_operations proc_net_operations = {
.read = generic_read_dir,
.readdir = proc_tgid_net_readdir,
};
struct proc_dir_entry *proc_net_fops_create(struct net *net,
const char *name, mode_t mode, const struct file_operations *fops)
@ -83,14 +159,6 @@ struct net *get_proc_net(const struct inode *inode)
}
EXPORT_SYMBOL_GPL(get_proc_net);
static struct proc_dir_entry *shadow_pde;
static struct proc_dir_entry *proc_net_shadow(struct task_struct *task,
struct proc_dir_entry *de)
{
return task->nsproxy->net_ns->proc_net;
}
struct proc_dir_entry *proc_net_mkdir(struct net *net, const char *name,
struct proc_dir_entry *parent)
{
@ -104,45 +172,39 @@ EXPORT_SYMBOL_GPL(proc_net_mkdir);
static __net_init int proc_net_ns_init(struct net *net)
{
struct proc_dir_entry *root, *netd, *net_statd;
struct proc_dir_entry *netd, *net_statd;
int err;
err = -ENOMEM;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
netd = kzalloc(sizeof(*netd), GFP_KERNEL);
if (!netd)
goto out;
err = -EEXIST;
netd = proc_net_mkdir(net, "net", root);
if (!netd)
goto free_root;
netd->data = net;
netd->nlink = 2;
netd->name = "net";
netd->namelen = 3;
netd->parent = &proc_root;
err = -EEXIST;
net_statd = proc_net_mkdir(net, "stat", netd);
if (!net_statd)
goto free_net;
root->data = net;
net->proc_net_root = root;
net->proc_net = netd;
net->proc_net_stat = net_statd;
err = 0;
return 0;
free_net:
kfree(netd);
out:
return err;
free_net:
remove_proc_entry("net", root);
free_root:
kfree(root);
goto out;
}
static __net_exit void proc_net_ns_exit(struct net *net)
{
remove_proc_entry("stat", net->proc_net);
remove_proc_entry("net", net->proc_net_root);
kfree(net->proc_net_root);
kfree(net->proc_net);
}
static struct pernet_operations __net_initdata proc_net_ns_ops = {
@ -152,8 +214,7 @@ static struct pernet_operations __net_initdata proc_net_ns_ops = {
int __init proc_net_init(void)
{
shadow_pde = proc_mkdir("net", NULL);
shadow_pde->shadow_proc = proc_net_shadow;
proc_symlink("net", NULL, "self/net");
return register_pernet_subsys(&proc_net_ns_ops);
}

3
include/linux/proc_fs.h
View File

@ -50,8 +50,6 @@ typedef int (read_proc_t)(char *page, char **start, off_t off,
typedef int (write_proc_t)(struct file *file, const char __user *buffer,
unsigned long count, void *data);
typedef int (get_info_t)(char *, char **, off_t, int);
typedef struct proc_dir_entry *(shadow_proc_t)(struct task_struct *task,
struct proc_dir_entry *pde);
struct proc_dir_entry {
unsigned int low_ino;
@ -82,7 +80,6 @@ struct proc_dir_entry {
int pde_users; /* number of callers into module in progress */
spinlock_t pde_unload_lock; /* proc_fops checks and pde_users bumps */
struct completion *pde_unload_completion;
shadow_proc_t *shadow_proc;
};
struct kcore_list {

1
include/net/net_namespace.h
View File

@ -31,7 +31,6 @@ struct net {
struct proc_dir_entry *proc_net;
struct proc_dir_entry *proc_net_stat;
struct proc_dir_entry *proc_net_root;
struct list_head sysctl_table_headers;