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[NETNS]: Fix /proc/net breakage 

Well I clearly goofed when I added the initial network namespace support
for /proc/net.  Currently things work but there are odd details visible to
user space, even when we have a single network namespace.

Since we do not cache proc_dir_entry dentries at the moment we can just
modify ->lookup to return a different directory inode depending on the
network namespace of the process looking at /proc/net, replacing the
current technique of using a magic and fragile follow_link method.

To accomplish that this patch:
- introduces a shadow_proc method to allow different dentries to
  be returned from proc_lookup.
- Removes the old /proc/net follow_link magic
- Fixes a weakness in our not caching of proc generic dentries.

As shadow_proc uses a task struct to decided which dentry to return we can
go back later and fix the proc generic caching without modifying any code
that uses the shadow_proc method.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric W. Biederman 2007-12-02 00:33:17 +11:00 committed by Herbert Xu
parent e03ba84adb
commit 2b1e300a9d
3 changed files with 19 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
fs/proc/generic.c
View File

@ -374,9 +374,16 @@ static int proc_delete_dentry(struct dentry * dentry)
return 1;
}
static int proc_revalidate_dentry(struct dentry *dentry, struct nameidata *nd)
{
d_drop(dentry);
return 0;
}
static struct dentry_operations proc_dentry_operations =
{
.d_delete = proc_delete_dentry,
.d_revalidate = proc_revalidate_dentry,
};
/*
@ -397,8 +404,11 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
if (de->namelen != dentry->d_name.len)
continue;
if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
unsigned int ino = de->low_ino;
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);
error = -EINVAL;

86
fs/proc/proc_net.c
View File

@ -50,89 +50,14 @@ struct net *get_proc_net(const struct inode *inode)
}
EXPORT_SYMBOL_GPL(get_proc_net);
static struct proc_dir_entry *proc_net_shadow;
static struct proc_dir_entry *shadow_pde;
static struct dentry *proc_net_shadow_dentry(struct dentry *parent,
static struct proc_dir_entry *proc_net_shadow(struct task_struct *task,
struct proc_dir_entry *de)
{
struct dentry *shadow = NULL;
struct inode *inode;
if (!de)
goto out;
de_get(de);
inode = proc_get_inode(parent->d_inode->i_sb, de->low_ino, de);
if (!inode)
goto out_de_put;
shadow = d_alloc_name(parent, de->name);
if (!shadow)
goto out_iput;
shadow->d_op = parent->d_op; /* proc_dentry_operations */
d_instantiate(shadow, inode);
out:
return shadow;
out_iput:
iput(inode);
out_de_put:
de_put(de);
goto out;
return task->nsproxy->net_ns->proc_net;
}
static void *proc_net_follow_link(struct dentry *parent, struct nameidata *nd)
{
struct net *net = current->nsproxy->net_ns;
struct dentry *shadow;
shadow = proc_net_shadow_dentry(parent, net->proc_net);
if (!shadow)
return ERR_PTR(-ENOENT);
dput(nd->dentry);
/* My dentry count is 1 and that should be enough as the
* shadow dentry is thrown away immediately.
*/
nd->dentry = shadow;
return NULL;
}
static struct dentry *proc_net_lookup(struct inode *dir, struct dentry *dentry,
struct nameidata *nd)
{
struct net *net = current->nsproxy->net_ns;
struct dentry *shadow;
shadow = proc_net_shadow_dentry(nd->dentry, net->proc_net);
if (!shadow)
return ERR_PTR(-ENOENT);
dput(nd->dentry);
nd->dentry = shadow;
return shadow->d_inode->i_op->lookup(shadow->d_inode, dentry, nd);
}
static int proc_net_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct net *net = current->nsproxy->net_ns;
struct dentry *shadow;
int ret;
shadow = proc_net_shadow_dentry(dentry->d_parent, net->proc_net);
if (!shadow)
return -ENOENT;
ret = shadow->d_inode->i_op->setattr(shadow, iattr);
dput(shadow);
return ret;
}
static const struct file_operations proc_net_dir_operations = {
.read = generic_read_dir,
};
static struct inode_operations proc_net_dir_inode_operations = {
.follow_link = proc_net_follow_link,
.lookup = proc_net_lookup,
.setattr = proc_net_setattr,
};
static __net_init int proc_net_ns_init(struct net *net)
{
struct proc_dir_entry *root, *netd, *net_statd;
@ -185,9 +110,8 @@ static struct pernet_operations __net_initdata proc_net_ns_ops = {
int __init proc_net_init(void)
{
proc_net_shadow = proc_mkdir("net", NULL);
proc_net_shadow->proc_iops = &proc_net_dir_inode_operations;
proc_net_shadow->proc_fops = &proc_net_dir_operations;
shadow_pde = proc_mkdir("net", NULL);
shadow_pde->shadow_proc = proc_net_shadow;
return register_pernet_subsys(&proc_net_ns_ops);
}

3
include/linux/proc_fs.h
View File

@ -48,6 +48,8 @@ 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;
@ -79,6 +81,7 @@ 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 {