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

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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
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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