Commit e9720acd authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller
Browse files

[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: default avatarStephen 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: default avatarPavel Emelyanov <xemul@openvz.org>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1ff82fe0

fs/proc/base.c

+1 −0
Original line number Diff line number Diff line
@@ -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),

fs/proc/generic.c

+17 −9
Original line number Diff line number Diff line
@@ -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

fs/proc/internal.h

+7 −0
Original line number Diff line number Diff line
@@ -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);

fs/proc/proc_net.c

+89 −28
Original line number Diff line number Diff line
@@ -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);

}

include/linux/proc_fs.h

+0 −3
Original line number Diff line number Diff line
@@ -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 {

CRA Git | Maintained and supported by SUSTech CRA and CCSE