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Subject[PATCH 4/7] proc: Make /proc/net it's own filesystem

Make the VFS happy with /proc/net by making it it's own
filesystem avoiding issues with hard links to directories
and other silliness that confuse the vfs today.

We preserve backwards compatibility by automatically
mounting /proc/self/net and marking it as a shrinkable
mount so userspace doesn't need to care about it.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
---
fs/proc/base.c | 6 +-
fs/proc/proc_net.c | 212 +++++++++++++++++++++++++++++++------------
include/linux/magic.h | 1 +
include/net/net_namespace.h | 1 +
security/selinux/hooks.c | 28 +++++-
5 files changed, 183 insertions(+), 65 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 486cf3f..9a68fa4 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -128,6 +128,10 @@ struct pid_entry {
NOD(NAME, (S_IFREG|(MODE)), \
NULL, &proc_single_file_operations, \
{ .proc_show = &proc_##OTYPE } )
+#define MNT(NAME, MODE, OTYPE) \
+ NOD(NAME, (S_IFDIR|(MODE)), \
+ &proc_##OTYPE##_inode_operations, NULL, \
+ {} )

/*
* Count the number of hardlinks for the pid_entry table, excluding the .
@@ -2453,7 +2457,7 @@ static const struct pid_entry tgid_base_stuff[] = {
DIR("fd", S_IRUSR|S_IXUSR, fd),
DIR("fdinfo", S_IRUSR|S_IXUSR, fdinfo),
#ifdef CONFIG_NET
- DIR("net", S_IRUGO|S_IXUGO, net),
+ MNT("net", S_IRUGO|S_IXUGO, net),
#endif
REG("environ", S_IRUSR, environ),
INF("auxv", S_IRUSR, pid_auxv),
diff --git a/fs/proc/proc_net.c b/fs/proc/proc_net.c
index 7bc296f..57e0f22 100644
--- a/fs/proc/proc_net.c
+++ b/fs/proc/proc_net.c
@@ -21,11 +21,13 @@
#include <linux/smp_lock.h>
#include <linux/mount.h>
#include <linux/nsproxy.h>
+#include <linux/namei.h>
#include <net/net_namespace.h>
#include <linux/seq_file.h>

#include "internal.h"

+static struct file_system_type proc_net_fs_type;

static struct net *get_proc_net(const struct inode *inode)
{
@@ -118,65 +120,60 @@ static struct net *get_proc_task_net(struct inode *dir)
return net;
}

-static struct dentry *proc_tgid_net_lookup(struct inode *dir,
- struct dentry *dentry, struct nameidata *nd)
+void *proc_net_follow_link(struct dentry *dentry, struct nameidata *nd)
{
- struct dentry *de;
+ /* Follow to a mount point of the proper network namespace.
+ */
+ struct vfsmount *mnt;
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);
+ int err = -ENOENT;
+
+ /* Which network namespace? */
+ net = get_proc_task_net(dentry->d_inode);
+ if (!net)
+ goto out_err;
+
+ /* Create a new mount. */
+ mnt = kern_mount_data(&proc_net_fs_type, net);
+ if (IS_ERR(mnt))
+ goto out_err;
+
+ dput(nd->path.dentry);
+ nd->path.dentry = dget(dentry);
+
+ /* Add mnt the mount namespace */
+ err = do_add_mount(mntget(mnt), &nd->path, MNT_SHRINKABLE,
+ &proc_automounts);
+ if (err < 0) {
+ mntput(mnt);
+ if (err == -EBUSY)
+ goto out_follow;
+ goto out_err;
}
- 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;
+ /* Place the mnt on path and return it to the caller */
+ err = 0;
+ path_put(&nd->path);
+ nd->path.mnt = mnt;
+ nd->path.dentry = dget(mnt->mnt_root);
+ put_net(net);
+out:
+ return ERR_PTR(err);
+out_err:
+ path_put(&nd->path);
+ goto out;
+out_follow:
+ /* We raced with ourselves so just walk the mounts */
+ while (d_mountpoint(nd->path.dentry) &&
+ follow_down(&nd->path.mnt, &nd->path.dentry))
+ ;
+ err = 0;
+ goto out;
}

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,
+ .follow_link = proc_net_follow_link,
};

-
struct proc_dir_entry *proc_net_fops_create(struct net *net,
const char *name, mode_t mode, const struct file_operations *fops)
{
@@ -190,21 +187,95 @@ void proc_net_remove(struct net *net, const char *name)
}
EXPORT_SYMBOL_GPL(proc_net_remove);

+
+static int proc_net_fill_super(struct super_block *sb)
+{
+ struct net *net = sb->s_fs_info;
+ struct proc_dir_entry *netd = net->proc_net;
+ struct inode *root_inode = NULL;
+
+ sb->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+ sb->s_magic = PROC_NET_SUPER_MAGIC;
+ sb->s_op = &proc_sops;
+ sb->s_time_gran = 1;
+
+ de_get(netd);
+ root_inode = proc_get_inode(sb, netd->low_ino, netd);
+ if (!root_inode)
+ goto out_no_root;
+ root_inode->i_uid = 0;
+ root_inode->i_gid = 0;
+ sb->s_root = d_alloc_root(root_inode);
+ if (!sb->s_root)
+ goto out_no_root;
+ return 0;
+
+out_no_root:
+ printk("%s: get root inode failed\n", __func__);
+ iput(root_inode);
+ de_put(netd);
+ return -ENOMEM;
+}
+
+static int proc_net_test_super(struct super_block *sb, void *data)
+{
+ return sb->s_fs_info == data;
+}
+
+static int proc_net_set_super(struct super_block *sb, void *data)
+{
+ sb->s_fs_info = data;
+ return set_anon_super(sb, NULL);
+}
+
+static int proc_net_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data, struct vfsmount *mnt)
+{
+ struct super_block *sb;
+
+ if (!(flags & MS_KERNMOUNT))
+ data = current->nsproxy->net_ns;
+
+ sb = sget(fs_type, proc_net_test_super, proc_net_set_super, data);
+ if (IS_ERR(sb))
+ return PTR_ERR(sb);
+
+ if (!sb->s_root) {
+ int err;
+ sb->s_flags = flags;
+ err = proc_net_fill_super(sb);
+ if (err) {
+ up_write(&sb->s_umount);
+ deactivate_super(sb);
+ return err;
+ }
+
+ sb->s_flags |= MS_ACTIVE;
+ }
+
+ return simple_set_mnt(mnt, sb);
+}
+
+static struct file_system_type proc_net_fs_type = {
+ .name = "proc/net",
+ .get_sb = proc_net_get_sb,
+ .kill_sb = kill_litter_super,
+};
+
static __net_init int proc_net_ns_init(struct net *net)
{
struct proc_dir_entry *netd, *net_statd;
+ struct vfsmount *mnt;
int err;

err = -ENOMEM;
- netd = kzalloc(sizeof(*netd), GFP_KERNEL);
+ netd = proc_create_root();
if (!netd)
goto out;

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);
@@ -213,8 +284,17 @@ static __net_init int proc_net_ns_init(struct net *net)

net->proc_net = netd;
net->proc_net_stat = net_statd;
+
+ mnt = kern_mount_data(&proc_net_fs_type, net);
+ if (IS_ERR(mnt))
+ goto free_stat;
+
+ net->proc_mnt = mnt;
+
return 0;

+free_stat:
+ remove_proc_entry("stat", netd);
free_net:
kfree(netd);
out:
@@ -224,7 +304,14 @@ out:
static __net_exit void proc_net_ns_exit(struct net *net)
{
remove_proc_entry("stat", net->proc_net);
- kfree(net->proc_net);
+ release_proc_entry(net->proc_net);
+ /* We won't be looking up this super block
+ * any more so set s_fs_info to NULL to ensure
+ * it doesn't conflict with network namespaces
+ * allocated in the future at the same address.
+ */
+ net->proc_mnt->mnt_sb->s_fs_info = NULL;
+ mntput(net->proc_mnt);
}

static struct pernet_operations __net_initdata proc_net_ns_ops = {
@@ -234,7 +321,16 @@ static struct pernet_operations __net_initdata proc_net_ns_ops = {

int __init proc_net_init(void)
{
- proc_symlink("net", NULL, "self/net");
+ struct proc_dir_entry *ent;
+ int err;
+
+ ent = proc_symlink("net", NULL, "self/net");
+ if (!ent)
+ return -EEXIST;
+
+ err = register_filesystem(&proc_net_fs_type);
+ if (err)
+ return err;

return register_pernet_subsys(&proc_net_ns_ops);
}
diff --git a/include/linux/magic.h b/include/linux/magic.h
index f7f3fdd..2b31c02 100644
--- a/include/linux/magic.h
+++ b/include/linux/magic.h
@@ -30,6 +30,7 @@
#define NFS_SUPER_MAGIC 0x6969
#define OPENPROM_SUPER_MAGIC 0x9fa1
#define PROC_SUPER_MAGIC 0x9fa0
+#define PROC_NET_SUPER_MAGIC 0x706e6574
#define QNX4_SUPER_MAGIC 0x002f /* qnx4 fs detection */

#define REISERFS_SUPER_MAGIC 0x52654973 /* used by gcc */
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 700c53a..77aba2b 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -40,6 +40,7 @@ struct net {

struct proc_dir_entry *proc_net;
struct proc_dir_entry *proc_net_stat;
+ struct vfsmount *proc_mnt;

#ifdef CONFIG_SYSCTL
struct ctl_table_set sysctls;
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f85597a..b38a2df 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -667,7 +667,7 @@ static int selinux_set_mnt_opts(struct super_block *sb,
goto out;
}

- if (strcmp(sb->s_type->name, "proc") == 0)
+ if (strncmp(sb->s_type->name, "proc", 4) == 0)
sbsec->proc = 1;

/* Determine the labeling behavior to use for this filesystem type. */
@@ -1116,16 +1116,18 @@ static inline u16 socket_type_to_security_class(int family, int type, int protoc
}

#ifdef CONFIG_PROC_FS
-static int selinux_proc_get_sid(struct proc_dir_entry *de,
+static int selinux_proc_get_sid(struct super_block *sb,
+ struct proc_dir_entry *de,
u16 tclass,
u32 *sid)
{
int buflen, rc;
char *buffer, *path, *end;

+ rc = -ENOMEM;
buffer = (char *)__get_free_page(GFP_KERNEL);
if (!buffer)
- return -ENOMEM;
+ goto out;

buflen = PAGE_SIZE;
end = buffer+buflen;
@@ -1136,19 +1138,32 @@ static int selinux_proc_get_sid(struct proc_dir_entry *de,
while (de && de != de->parent) {
buflen -= de->namelen + 1;
if (buflen < 0)
- break;
+ goto out_free;
end -= de->namelen;
memcpy(end, de->name, de->namelen);
*--end = '/';
path = end;
de = de->parent;
}
+ if (strcmp(sb->type->name, "proc") != 0) {
+ const char *name = sb->type->name + 4;
+ int namelen = strlen(name);
+ buflen -= namelen;
+ if (buflen < 0)
+ goto out_free;
+ end -= namelen;
+ memcpy(end, name);
+ path = end;
+ }
rc = security_genfs_sid("proc", path, tclass, sid);
+out_free:
free_page((unsigned long)buffer);
+out:
return rc;
}
#else
-static int selinux_proc_get_sid(struct proc_dir_entry *de,
+static int selinux_proc_get_sid(struct super_block *sb,
+ struct proc_dir_entry *de,
u16 tclass,
u32 *sid)
{
@@ -1297,7 +1312,8 @@ static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dent
struct proc_inode *proci = PROC_I(inode);
if (proci->pde) {
isec->sclass = inode_mode_to_security_class(inode->i_mode);
- rc = selinux_proc_get_sid(proci->pde,
+ rc = selinux_proc_get_sid(inode->i_sb,
+ proci->pde,
isec->sclass,
&sid);
if (rc)
--
1.5.3.rc6.17.g1911


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