kernel-ark/fs/proc/proc_net.c
Alexey Dobriyan 2d3a4e3666 proc: fix ->open'less usage due to ->proc_fops flip
Typical PDE creation code looks like:

	pde = create_proc_entry("foo", 0, NULL);
	if (pde)
		pde->proc_fops = &foo_proc_fops;

Notice that PDE is first created, only then ->proc_fops is set up to
final value. This is a problem because right after creation
a) PDE is fully visible in /proc , and
b) ->proc_fops are proc_file_operations which do not have ->open callback. So, it's
   possible to ->read without ->open (see one class of oopses below).

The fix is new API called proc_create() which makes sure ->proc_fops are
set up before gluing PDE to main tree. Typical new code looks like:

	pde = proc_create("foo", 0, NULL, &foo_proc_fops);
	if (!pde)
		return -ENOMEM;

Fix most networking users for a start.

In the long run, create_proc_entry() for regular files will go.

BUG: unable to handle kernel NULL pointer dereference at virtual address 00000024
printing eip: c1188c1b *pdpt = 000000002929e001 *pde = 0000000000000000
Oops: 0002 [#1] PREEMPT SMP DEBUG_PAGEALLOC
last sysfs file: /sys/block/sda/sda1/dev
Modules linked in: foo af_packet ipv6 cpufreq_ondemand loop serio_raw psmouse k8temp hwmon sr_mod cdrom

Pid: 24679, comm: cat Not tainted (2.6.24-rc3-mm1 #2)
EIP: 0060:[<c1188c1b>] EFLAGS: 00210002 CPU: 0
EIP is at mutex_lock_nested+0x75/0x25d
EAX: 000006fe EBX: fffffffb ECX: 00001000 EDX: e9340570
ESI: 00000020 EDI: 00200246 EBP: e9340570 ESP: e8ea1ef8
 DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Process cat (pid: 24679, ti=E8EA1000 task=E9340570 task.ti=E8EA1000)
Stack: 00000000 c106f7ce e8ee05b4 00000000 00000001 458003d0 f6fb6f20 fffffffb
       00000000 c106f7aa 00001000 c106f7ce 08ae9000 f6db53f0 00000020 00200246
       00000000 00000002 00000000 00200246 00200246 e8ee05a0 fffffffb e8ee0550
Call Trace:
 [<c106f7ce>] seq_read+0x24/0x28a
 [<c106f7aa>] seq_read+0x0/0x28a
 [<c106f7ce>] seq_read+0x24/0x28a
 [<c106f7aa>] seq_read+0x0/0x28a
 [<c10818b8>] proc_reg_read+0x60/0x73
 [<c1081858>] proc_reg_read+0x0/0x73
 [<c105a34f>] vfs_read+0x6c/0x8b
 [<c105a6f3>] sys_read+0x3c/0x63
 [<c10025f2>] sysenter_past_esp+0x5f/0xa5
 [<c10697a7>] destroy_inode+0x24/0x33
 =======================
INFO: lockdep is turned off.
Code: 75 21 68 e1 1a 19 c1 68 87 00 00 00 68 b8 e8 1f c1 68 25 73 1f c1 e8 84 06 e9 ff e8 52 b8 e7 ff 83 c4 10 9c 5f fa e8 28 89 ea ff <f0> fe 4e 04 79 0a f3 90 80 7e 04 00 7e f8 eb f0 39 76 34 74 33
EIP: [<c1188c1b>] mutex_lock_nested+0x75/0x25d SS:ESP 0068:e8ea1ef8

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:24 -08:00

160 lines
3.2 KiB
C

/*
* linux/fs/proc/net.c
*
* Copyright (C) 2007
*
* Author: Eric Biederman <ebiederm@xmission.com>
*
* proc net directory handling functions
*/
#include <asm/uaccess.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/smp_lock.h>
#include <linux/mount.h>
#include <linux/nsproxy.h>
#include <net/net_namespace.h>
#include <linux/seq_file.h>
#include "internal.h"
int seq_open_net(struct inode *ino, struct file *f,
const struct seq_operations *ops, int size)
{
struct net *net;
struct seq_net_private *p;
BUG_ON(size < sizeof(*p));
net = get_proc_net(ino);
if (net == NULL)
return -ENXIO;
p = __seq_open_private(f, ops, size);
if (p == NULL) {
put_net(net);
return -ENOMEM;
}
p->net = net;
return 0;
}
EXPORT_SYMBOL_GPL(seq_open_net);
int seq_release_net(struct inode *ino, struct file *f)
{
struct seq_file *seq;
struct seq_net_private *p;
seq = f->private_data;
p = seq->private;
put_net(p->net);
seq_release_private(ino, f);
return 0;
}
EXPORT_SYMBOL_GPL(seq_release_net);
struct proc_dir_entry *proc_net_fops_create(struct net *net,
const char *name, mode_t mode, const struct file_operations *fops)
{
return proc_create(name, mode, net->proc_net, fops);
}
EXPORT_SYMBOL_GPL(proc_net_fops_create);
void proc_net_remove(struct net *net, const char *name)
{
remove_proc_entry(name, net->proc_net);
}
EXPORT_SYMBOL_GPL(proc_net_remove);
struct net *get_proc_net(const struct inode *inode)
{
return maybe_get_net(PDE_NET(PDE(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)
{
struct proc_dir_entry *pde;
pde = proc_mkdir_mode(name, S_IRUGO | S_IXUGO, parent);
if (pde != NULL)
pde->data = net;
return pde;
}
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;
int err;
err = -ENOMEM;
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root)
goto out;
err = -EEXIST;
netd = proc_net_mkdir(net, "net", root);
if (!netd)
goto free_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;
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);
}
static struct pernet_operations __net_initdata proc_net_ns_ops = {
.init = proc_net_ns_init,
.exit = proc_net_ns_exit,
};
int __init proc_net_init(void)
{
shadow_pde = proc_mkdir("net", NULL);
shadow_pde->shadow_proc = proc_net_shadow;
return register_pernet_subsys(&proc_net_ns_ops);
}