[PATCH] Make /proc/net a symlink on /proc/self/net (v3)
From: Pavel Emelyanov
Date: Fri Mar 07 2008 - 09:05:17 EST
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@xxxxxxxxxxxxx>
Changes from v1:
* Fixed a task_struct leak in get_proc_task_net, pointed out by Paul.
Signed-off-by: Pavel Emelyanov <xemul@xxxxxxxxxx>
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 96ee899..cc43cf0 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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),
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 68971e6..a36ad3c 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -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
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index 1c81c8f..bc72f5c 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -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);
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 14e9b5a..4caa5f7 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -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);
}
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index d9a9e71..9b6c935 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -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 {
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 28738b7..923f2b8 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -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;
--
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