[PATCH] proc: move proc mount options out of pid_namespace

[PATCH] proc: move proc mount options out of pid_namespace

[Stephen Mell]

From: Stephen Mell <sub.atomic.fusion@gmail.com>

hide_pid and pid_gid are proc mount options whose values are stored in the pid_namespace struct. As a result, if one mounts proc again for the same PID namespace with different mount options, all mounts for that PID namespace will be affected. This seems undesirable. This patch creates a proc_sb_info struct that points to the applicable PID namespace, and it moves hide_pid, pid_gid, and proc_self from pid_namespace to proc_sb_info.

Signed-off-by: Stephen Mell <sub.atomic.fusion@gmail.com>
---
diff --git a/fs/proc/base.c b/fs/proc/base.c
index dd51e50..853eb68 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -584,13 +584,13 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr)
  * May current process learn task's sched/cmdline info (for hide_pid_min=1)
  * or euid/egid (for hide_pid_min=2)?
  */
-static bool has_pid_permissions(struct pid_namespace *pid,
+static bool has_pid_permissions(struct proc_sb_info *fsi,
 				 struct task_struct *task,
 				 int hide_pid_min)
 {
-	if (pid->hide_pid < hide_pid_min)
+	if (fsi->hide_pid < hide_pid_min)
 		return true;
-	if (in_group_p(pid->pid_gid))
+	if (in_group_p(fsi->pid_gid))
 		return true;
 	return ptrace_may_access(task, PTRACE_MODE_READ);
 }
@@ -598,18 +598,18 @@ static bool has_pid_permissions(struct pid_namespace *pid,
 
 static int proc_pid_permission(struct inode *inode, int mask)
 {
-	struct pid_namespace *pid = inode->i_sb->s_fs_info;
+	struct proc_sb_info *fsi = inode->i_sb->s_fs_info;
 	struct task_struct *task;
 	bool has_perms;
 
 	task = get_proc_task(inode);
 	if (!task)
 		return -ESRCH;
-	has_perms = has_pid_permissions(pid, task, 1);
+	has_perms = has_pid_permissions(fsi, task, 1);
 	put_task_struct(task);
 
 	if (!has_perms) {
-		if (pid->hide_pid == 2) {
+		if (fsi->hide_pid == 2) {
 			/*
 			 * Let's make getdents(), stat(), and open()
 			 * consistent with each other.  If a process
@@ -670,12 +670,14 @@ static const struct file_operations proc_info_file_operations = {
 static int proc_single_show(struct seq_file *m, void *v)
 {
 	struct inode *inode = m->private;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 	struct pid *pid;
 	struct task_struct *task;
 	int ret;
 
-	ns = inode->i_sb->s_fs_info;
+	fsi = inode->i_sb->s_fs_info;
+	ns = fsi->ns;
 	pid = proc_pid(inode);
 	task = get_pid_task(pid, PIDTYPE_PID);
 	if (!task)
@@ -1574,7 +1576,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	struct inode *inode = dentry->d_inode;
 	struct task_struct *task;
 	const struct cred *cred;
-	struct pid_namespace *pid = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
 
 	generic_fillattr(inode, stat);
 
@@ -1583,7 +1585,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	stat->gid = GLOBAL_ROOT_GID;
 	task = pid_task(proc_pid(inode), PIDTYPE_PID);
 	if (task) {
-		if (!has_pid_permissions(pid, task, 2)) {
+		if (!has_pid_permissions(fsi, task, 2)) {
 			rcu_read_unlock();
 			/*
 			 * This doesn't prevent learning whether PID exists,
@@ -2869,13 +2871,15 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign
 	struct dentry *result = NULL;
 	struct task_struct *task;
 	unsigned tgid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	tgid = name_to_int(dentry);
 	if (tgid == ~0U)
 		goto out;
 
-	ns = dentry->d_sb->s_fs_info;
+	fsi = dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	rcu_read_lock();
 	task = find_task_by_pid_ns(tgid, ns);
 	if (task)
@@ -2954,6 +2958,7 @@ static int fake_filldir(void *buf, const char *name, int namelen,
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
 	struct tgid_iter iter;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 	filldir_t __filldir;
 	loff_t pos = filp->f_pos;
@@ -2970,11 +2975,12 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 		iter.tgid = pos - TGID_OFFSET;
 	}
 	iter.task = NULL;
-	ns = filp->f_dentry->d_sb->s_fs_info;
+	fsi = filp->f_dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	for (iter = next_tgid(ns, iter);
 	     iter.task;
 	     iter.tgid += 1, iter = next_tgid(ns, iter)) {
-		if (has_pid_permissions(ns, iter.task, 2))
+		if (has_pid_permissions(fsi, iter.task, 2))
 			__filldir = filldir;
 		else
 			__filldir = fake_filldir;
@@ -3132,6 +3138,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
 	struct task_struct *task;
 	struct task_struct *leader = get_proc_task(dir);
 	unsigned tid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	if (!leader)
@@ -3141,7 +3148,8 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
 	if (tid == ~0U)
 		goto out;
 
-	ns = dentry->d_sb->s_fs_info;
+	fsi = dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	rcu_read_lock();
 	task = find_task_by_pid_ns(tid, ns);
 	if (task)
@@ -3249,6 +3257,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
 	int retval = -ENOENT;
 	ino_t ino;
 	int tid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	task = get_proc_task(inode);
@@ -3283,7 +3292,8 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
 	/* f_version caches the tgid value that the last readdir call couldn't
 	 * return. lseek aka telldir automagically resets f_version to 0.
 	 */
-	ns = filp->f_dentry->d_sb->s_fs_info;
+	fsi = filp->f_dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	tid = (int)filp->f_version;
 	filp->f_version = 0;
 	for (task = first_tid(leader, tid, filp->f_pos - 2, ns);
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 073aea6..148737d 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -110,12 +110,12 @@ void __init proc_init_inodecache(void)
 static int proc_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
-	struct pid_namespace *pid = sb->s_fs_info;
+	struct proc_sb_info *fsi = sb->s_fs_info;
 
-	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
-		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
-	if (pid->hide_pid != 0)
-		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
+	if (!gid_eq(fsi->pid_gid, GLOBAL_ROOT_GID))
+		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fsi->pid_gid));
+	if (fsi->hide_pid != 0)
+		seq_printf(seq, ",hidepid=%u", fsi->hide_pid);
 
 	return 0;
 }
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index d600fb0..ff970e4 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -29,6 +29,14 @@ struct mempolicy;
  * /proc file has a parent, but "subdir" is NULL for all
  * non-directory entries).
  */
+
+struct proc_sb_info {
+	struct pid_namespace *ns;
+	struct dentry *proc_self;
+	kgid_t pid_gid;
+	int hide_pid;
+};
+
 struct proc_dir_entry {
 	unsigned int low_ino;
 	umode_t mode;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 41a6ea9..526aec6 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -20,6 +20,7 @@
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
 #include <linux/parser.h>
+#include <linux/slab.h>
 
 #include "internal.h"
 
@@ -31,10 +32,9 @@ static int proc_test_super(struct super_block *sb, void *data)
 static int proc_set_super(struct super_block *sb, void *data)
 {
 	int err = set_anon_super(sb, NULL);
-	if (!err) {
-		struct pid_namespace *ns = (struct pid_namespace *)data;
-		sb->s_fs_info = get_pid_ns(ns);
-	}
+	if (!err)
+		sb->s_fs_info = (struct proc_sb_info *)data;
+
 	return err;
 }
 
@@ -48,7 +48,7 @@ static const match_table_t tokens = {
 	{Opt_err, NULL},
 };
 
-static int proc_parse_options(char *options, struct pid_namespace *pid)
+static int proc_parse_options(char *options, struct proc_sb_info *fsi)
 {
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
@@ -68,7 +68,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 		case Opt_gid:
 			if (match_int(&args[0], &option))
 				return 0;
-			pid->pid_gid = make_kgid(current_user_ns(), option);
+			fsi->pid_gid = make_kgid(current_user_ns(), option);
 			break;
 		case Opt_hidepid:
 			if (match_int(&args[0], &option))
@@ -77,7 +77,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 				pr_err("proc: hidepid value must be between 0 and 2.\n");
 				return 0;
 			}
-			pid->hide_pid = option;
+			fsi->hide_pid = option;
 			break;
 		default:
 			pr_err("proc: unrecognized mount option \"%s\" "
@@ -91,36 +91,44 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 
 int proc_remount(struct super_block *sb, int *flags, char *data)
 {
-	struct pid_namespace *pid = sb->s_fs_info;
-	return !proc_parse_options(data, pid);
+	struct proc_sb_info *fsi = sb->s_fs_info;
+	return !proc_parse_options(data, fsi);
 }
 
 static struct dentry *proc_mount(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data)
 {
 	int err;
+	struct proc_sb_info *fsi;
 	struct super_block *sb;
-	struct pid_namespace *ns;
 	char *options;
+	
+	fsi = kzalloc(sizeof(struct proc_sb_info), GFP_KERNEL);
+	if (!fsi)
+		return ERR_PTR(-ENOMEM);
+
+	sb = sget(fs_type, proc_test_super, proc_set_super, flags, fsi);
+	if (IS_ERR(sb))
+		return ERR_CAST(sb);
 
 	if (flags & MS_KERNMOUNT) {
-		ns = (struct pid_namespace *)data;
+		fsi->ns = (struct pid_namespace *)data;
+		get_pid_ns(fsi->ns);
 		options = NULL;
 	} else {
-		ns = task_active_pid_ns(current);
-		options = data;
-
 		if (!current_user_ns()->may_mount_proc)
 			return ERR_PTR(-EPERM);
-	}
-
-	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
-	if (IS_ERR(sb))
-		return ERR_CAST(sb);
+		
+		options = data;
+		if (!proc_parse_options(options, fsi)) {
+			deactivate_locked_super(sb);
+			return ERR_PTR(-EINVAL);
+		}
 
-	if (!proc_parse_options(options, ns)) {
-		deactivate_locked_super(sb);
-		return ERR_PTR(-EINVAL);
+		if (!fsi->ns) {
+			fsi->ns = task_active_pid_ns(current);
+			get_pid_ns(fsi->ns);
+		}
 	}
 
 	if (!sb->s_root) {
@@ -138,13 +146,16 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 
 static void proc_kill_sb(struct super_block *sb)
 {
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
-	ns = (struct pid_namespace *)sb->s_fs_info;
-	if (ns->proc_self)
-		dput(ns->proc_self);
+	fsi = (struct proc_sb_info *)sb->s_fs_info;
+	ns = (struct pid_namespace *)fsi->ns;
+	if (fsi->proc_self)
+		dput(fsi->proc_self);
 	kill_anon_super(sb);
 	put_pid_ns(ns);
+	kfree(fsi);
 }
 
 static struct file_system_type proc_fs_type = {
diff --git a/fs/proc/self.c b/fs/proc/self.c
index 6b6a993..ff4a2e2 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -10,7 +10,8 @@
 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 			      int buflen)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = fsi->ns;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
 	if (!tgid)
@@ -21,7 +22,8 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = fsi->ns;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char *name = ERR_PTR(-ENOENT);
 	if (tgid) {
@@ -55,7 +57,7 @@ static unsigned self_inum;
 int proc_setup_self(struct super_block *s)
 {
 	struct inode *root_inode = s->s_root->d_inode;
-	struct pid_namespace *ns = s->s_fs_info;
+	struct proc_sb_info *fsi = s->s_fs_info;
 	struct dentry *self;
 	
 	mutex_lock(&root_inode->i_mutex);
@@ -82,7 +84,7 @@ int proc_setup_self(struct super_block *s)
 		pr_err("proc_fill_super: can't allocate /proc/self\n");
 		return PTR_ERR(self);
 	}
-	ns->proc_self = self;
+	fsi->proc_self = self;
 	return 0;
 }
 
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index e277266..6185386 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -31,15 +31,12 @@ struct pid_namespace {
 	struct pid_namespace *parent;
 #ifdef CONFIG_PROC_FS
 	struct vfsmount *proc_mnt;
-	struct dentry *proc_self;
 #endif
 #ifdef CONFIG_BSD_PROCESS_ACCT
 	struct bsd_acct_struct *bacct;
 #endif
 	struct user_namespace *user_ns;
 	struct work_struct proc_work;
-	kgid_t pid_gid;
-	int hide_pid;
 	int reboot;	/* group exit code if this pidns was rebooted */
 	unsigned int proc_inum;
 };

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Gu Zheng]

Hi Stephen,
	Refer to following inline comments.
Thanks,
Gu 

On 05/23/2013 04:05 PM, Stephen Mell wrote:

> From: Stephen Mell <sub.atomic.fusion@gmail.com>
> 
> hide_pid and pid_gid are proc mount options whose values are stored in the pid_namespace struct. As a result, if one mounts proc again for the same PID namespace with different mount options, all mounts for that PID namespace will be affected. This seems undesirable. This patch creates a proc_sb_info struct that points to the applicable PID namespace, and it moves hide_pid, pid_gid, and proc_self from pid_namespace to proc_sb_info.
> 
> Signed-off-by: Stephen Mell <sub.atomic.fusion@gmail.com>

Reviewed-by: Gu Zheng <guz.fnst@cn.fujitsu.com>

> ---
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index dd51e50..853eb68 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -584,13 +584,13 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr)
>   * May current process learn task's sched/cmdline info (for hide_pid_min=1)
>   * or euid/egid (for hide_pid_min=2)?
>   */
> -static bool has_pid_permissions(struct pid_namespace *pid,
> +static bool has_pid_permissions(struct proc_sb_info *fsi,
>  				 struct task_struct *task,
>  				 int hide_pid_min)
>  {
> -	if (pid->hide_pid < hide_pid_min)
> +	if (fsi->hide_pid < hide_pid_min)
>  		return true;
> -	if (in_group_p(pid->pid_gid))
> +	if (in_group_p(fsi->pid_gid))
>  		return true;
>  	return ptrace_may_access(task, PTRACE_MODE_READ);
>  }
> @@ -598,18 +598,18 @@ static bool has_pid_permissions(struct pid_namespace *pid,
>  
>  static int proc_pid_permission(struct inode *inode, int mask)
>  {
> -	struct pid_namespace *pid = inode->i_sb->s_fs_info;
> +	struct proc_sb_info *fsi = inode->i_sb->s_fs_info;
>  	struct task_struct *task;
>  	bool has_perms;
>  
>  	task = get_proc_task(inode);
>  	if (!task)
>  		return -ESRCH;
> -	has_perms = has_pid_permissions(pid, task, 1);
> +	has_perms = has_pid_permissions(fsi, task, 1);
>  	put_task_struct(task);
>  
>  	if (!has_perms) {
> -		if (pid->hide_pid == 2) {
> +		if (fsi->hide_pid == 2) {
>  			/*
>  			 * Let's make getdents(), stat(), and open()
>  			 * consistent with each other.  If a process
> @@ -670,12 +670,14 @@ static const struct file_operations proc_info_file_operations = {
>  static int proc_single_show(struct seq_file *m, void *v)
>  {
>  	struct inode *inode = m->private;
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  	struct pid *pid;
>  	struct task_struct *task;
>  	int ret;
>  
> -	ns = inode->i_sb->s_fs_info;
> +	fsi = inode->i_sb->s_fs_info;
> +	ns = fsi->ns;
>  	pid = proc_pid(inode);
>  	task = get_pid_task(pid, PIDTYPE_PID);
>  	if (!task)
> @@ -1574,7 +1576,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
>  	struct inode *inode = dentry->d_inode;
>  	struct task_struct *task;
>  	const struct cred *cred;
> -	struct pid_namespace *pid = dentry->d_sb->s_fs_info;
> +	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
>  
>  	generic_fillattr(inode, stat);
>  
> @@ -1583,7 +1585,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
>  	stat->gid = GLOBAL_ROOT_GID;
>  	task = pid_task(proc_pid(inode), PIDTYPE_PID);
>  	if (task) {
> -		if (!has_pid_permissions(pid, task, 2)) {
> +		if (!has_pid_permissions(fsi, task, 2)) {
>  			rcu_read_unlock();
>  			/*
>  			 * This doesn't prevent learning whether PID exists,
> @@ -2869,13 +2871,15 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign
>  	struct dentry *result = NULL;
>  	struct task_struct *task;
>  	unsigned tgid;
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  
>  	tgid = name_to_int(dentry);
>  	if (tgid == ~0U)
>  		goto out;
>  
> -	ns = dentry->d_sb->s_fs_info;
> +	fsi = dentry->d_sb->s_fs_info;
> +	ns = fsi->ns;
>  	rcu_read_lock();
>  	task = find_task_by_pid_ns(tgid, ns);
>  	if (task)
> @@ -2954,6 +2958,7 @@ static int fake_filldir(void *buf, const char *name, int namelen,
>  int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
>  {
>  	struct tgid_iter iter;
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  	filldir_t __filldir;
>  	loff_t pos = filp->f_pos;
> @@ -2970,11 +2975,12 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
>  		iter.tgid = pos - TGID_OFFSET;
>  	}
>  	iter.task = NULL;
> -	ns = filp->f_dentry->d_sb->s_fs_info;
> +	fsi = filp->f_dentry->d_sb->s_fs_info;
> +	ns = fsi->ns;
>  	for (iter = next_tgid(ns, iter);
>  	     iter.task;
>  	     iter.tgid += 1, iter = next_tgid(ns, iter)) {
> -		if (has_pid_permissions(ns, iter.task, 2))
> +		if (has_pid_permissions(fsi, iter.task, 2))
>  			__filldir = filldir;
>  		else
>  			__filldir = fake_filldir;
> @@ -3132,6 +3138,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
>  	struct task_struct *task;
>  	struct task_struct *leader = get_proc_task(dir);
>  	unsigned tid;
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  
>  	if (!leader)
> @@ -3141,7 +3148,8 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
>  	if (tid == ~0U)
>  		goto out;
>  
> -	ns = dentry->d_sb->s_fs_info;
> +	fsi = dentry->d_sb->s_fs_info;
> +	ns = fsi->ns;
>  	rcu_read_lock();
>  	task = find_task_by_pid_ns(tid, ns);
>  	if (task)
> @@ -3249,6 +3257,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
>  	int retval = -ENOENT;
>  	ino_t ino;
>  	int tid;
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  
>  	task = get_proc_task(inode);
> @@ -3283,7 +3292,8 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
>  	/* f_version caches the tgid value that the last readdir call couldn't
>  	 * return. lseek aka telldir automagically resets f_version to 0.
>  	 */
> -	ns = filp->f_dentry->d_sb->s_fs_info;
> +	fsi = filp->f_dentry->d_sb->s_fs_info;
> +	ns = fsi->ns;
>  	tid = (int)filp->f_version;
>  	filp->f_version = 0;
>  	for (task = first_tid(leader, tid, filp->f_pos - 2, ns);
> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
> index 073aea6..148737d 100644
> --- a/fs/proc/inode.c
> +++ b/fs/proc/inode.c
> @@ -110,12 +110,12 @@ void __init proc_init_inodecache(void)
>  static int proc_show_options(struct seq_file *seq, struct dentry *root)
>  {
>  	struct super_block *sb = root->d_sb;
> -	struct pid_namespace *pid = sb->s_fs_info;
> +	struct proc_sb_info *fsi = sb->s_fs_info;
>  
> -	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
> -		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
> -	if (pid->hide_pid != 0)
> -		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
> +	if (!gid_eq(fsi->pid_gid, GLOBAL_ROOT_GID))
> +		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fsi->pid_gid));
> +	if (fsi->hide_pid != 0)
> +		seq_printf(seq, ",hidepid=%u", fsi->hide_pid);
>  
>  	return 0;
>  }
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index d600fb0..ff970e4 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -29,6 +29,14 @@ struct mempolicy;
>   * /proc file has a parent, but "subdir" is NULL for all
>   * non-directory entries).
>   */
> +
> +struct proc_sb_info {
> +	struct pid_namespace *ns;
> +	struct dentry *proc_self;
> +	kgid_t pid_gid;
> +	int hide_pid;
> +};
> +
>  struct proc_dir_entry {
>  	unsigned int low_ino;
>  	umode_t mode;
> diff --git a/fs/proc/root.c b/fs/proc/root.c
> index 41a6ea9..526aec6 100644
> --- a/fs/proc/root.c
> +++ b/fs/proc/root.c
> @@ -20,6 +20,7 @@
>  #include <linux/mount.h>
>  #include <linux/pid_namespace.h>
>  #include <linux/parser.h>
> +#include <linux/slab.h>
>  
>  #include "internal.h"
>  
> @@ -31,10 +32,9 @@ static int proc_test_super(struct super_block *sb, void *data)
>  static int proc_set_super(struct super_block *sb, void *data)
>  {
>  	int err = set_anon_super(sb, NULL);
> -	if (!err) {
> -		struct pid_namespace *ns = (struct pid_namespace *)data;
> -		sb->s_fs_info = get_pid_ns(ns);
> -	}
> +	if (!err)
> +		sb->s_fs_info = (struct proc_sb_info *)data;
> +
>  	return err;
>  }
>  
> @@ -48,7 +48,7 @@ static const match_table_t tokens = {
>  	{Opt_err, NULL},
>  };
>  
> -static int proc_parse_options(char *options, struct pid_namespace *pid)
> +static int proc_parse_options(char *options, struct proc_sb_info *fsi)
>  {
>  	char *p;
>  	substring_t args[MAX_OPT_ARGS];
> @@ -68,7 +68,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
>  		case Opt_gid:
>  			if (match_int(&args[0], &option))
>  				return 0;
> -			pid->pid_gid = make_kgid(current_user_ns(), option);
> +			fsi->pid_gid = make_kgid(current_user_ns(), option);
>  			break;
>  		case Opt_hidepid:
>  			if (match_int(&args[0], &option))
> @@ -77,7 +77,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
>  				pr_err("proc: hidepid value must be between 0 and 2.\n");
>  				return 0;
>  			}
> -			pid->hide_pid = option;
> +			fsi->hide_pid = option;
>  			break;
>  		default:
>  			pr_err("proc: unrecognized mount option \"%s\" "
> @@ -91,36 +91,44 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
>  
>  int proc_remount(struct super_block *sb, int *flags, char *data)
>  {
> -	struct pid_namespace *pid = sb->s_fs_info;
> -	return !proc_parse_options(data, pid);
> +	struct proc_sb_info *fsi = sb->s_fs_info;
> +	return !proc_parse_options(data, fsi);
>  }
>  
>  static struct dentry *proc_mount(struct file_system_type *fs_type,
>  	int flags, const char *dev_name, void *data)
>  {
>  	int err;
> +	struct proc_sb_info *fsi;
>  	struct super_block *sb;
> -	struct pid_namespace *ns;
>  	char *options;
> +	
> +	fsi = kzalloc(sizeof(struct proc_sb_info), GFP_KERNEL);
> +	if (!fsi)
> +		return ERR_PTR(-ENOMEM);
> +
> +	sb = sget(fs_type, proc_test_super, proc_set_super, flags, fsi);


Here it'll create a new proc sb instance which holds the same context as the old ones
each time we mount proc though in the same PID namespace, won't it?

> +	if (IS_ERR(sb))
> +		return ERR_CAST(sb);
>  
>  	if (flags & MS_KERNMOUNT) {
> -		ns = (struct pid_namespace *)data;
> +		fsi->ns = (struct pid_namespace *)data;
> +		get_pid_ns(fsi->ns);
>  		options = NULL;
>  	} else {
> -		ns = task_active_pid_ns(current);
> -		options = data;
> -
>  		if (!current_user_ns()->may_mount_proc)
>  			return ERR_PTR(-EPERM);
> -	}
> -
> -	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
> -	if (IS_ERR(sb))
> -		return ERR_CAST(sb);
> +		
> +		options = data;
> +		if (!proc_parse_options(options, fsi)) {
> +			deactivate_locked_super(sb);
> +			return ERR_PTR(-EINVAL);
> +		}
>  
> -	if (!proc_parse_options(options, ns)) {
> -		deactivate_locked_super(sb);
> -		return ERR_PTR(-EINVAL);
> +		if (!fsi->ns) {
> +			fsi->ns = task_active_pid_ns(current);
> +			get_pid_ns(fsi->ns);
> +		}
>  	}
>  
>  	if (!sb->s_root) {
> @@ -138,13 +146,16 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
>  
>  static void proc_kill_sb(struct super_block *sb)
>  {
> +	struct proc_sb_info *fsi;
>  	struct pid_namespace *ns;
>  
> -	ns = (struct pid_namespace *)sb->s_fs_info;
> -	if (ns->proc_self)
> -		dput(ns->proc_self);
> +	fsi = (struct proc_sb_info *)sb->s_fs_info;
> +	ns = (struct pid_namespace *)fsi->ns;
> +	if (fsi->proc_self)


Here the pre-check seems needless.

> +		dput(fsi->proc_self);
>  	kill_anon_super(sb);
>  	put_pid_ns(ns);
> +	kfree(fsi);
>  }
>  
>  static struct file_system_type proc_fs_type = {
> diff --git a/fs/proc/self.c b/fs/proc/self.c
> index 6b6a993..ff4a2e2 100644
> --- a/fs/proc/self.c
> +++ b/fs/proc/self.c
> @@ -10,7 +10,8 @@
>  static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
>  			      int buflen)
>  {
> -	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
> +	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
> +	struct pid_namespace *ns = fsi->ns;
>  	pid_t tgid = task_tgid_nr_ns(current, ns);
>  	char tmp[PROC_NUMBUF];
>  	if (!tgid)
> @@ -21,7 +22,8 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
>  
>  static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
>  {
> -	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
> +	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
> +	struct pid_namespace *ns = fsi->ns;
>  	pid_t tgid = task_tgid_nr_ns(current, ns);
>  	char *name = ERR_PTR(-ENOENT);
>  	if (tgid) {
> @@ -55,7 +57,7 @@ static unsigned self_inum;
>  int proc_setup_self(struct super_block *s)
>  {
>  	struct inode *root_inode = s->s_root->d_inode;
> -	struct pid_namespace *ns = s->s_fs_info;
> +	struct proc_sb_info *fsi = s->s_fs_info;
>  	struct dentry *self;
>  	
>  	mutex_lock(&root_inode->i_mutex);
> @@ -82,7 +84,7 @@ int proc_setup_self(struct super_block *s)
>  		pr_err("proc_fill_super: can't allocate /proc/self\n");
>  		return PTR_ERR(self);
>  	}
> -	ns->proc_self = self;
> +	fsi->proc_self = self;
>  	return 0;
>  }
>  
> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> index e277266..6185386 100644
> --- a/include/linux/pid_namespace.h
> +++ b/include/linux/pid_namespace.h
> @@ -31,15 +31,12 @@ struct pid_namespace {
>  	struct pid_namespace *parent;
>  #ifdef CONFIG_PROC_FS
>  	struct vfsmount *proc_mnt;
> -	struct dentry *proc_self;
>  #endif
>  #ifdef CONFIG_BSD_PROCESS_ACCT
>  	struct bsd_acct_struct *bacct;
>  #endif
>  	struct user_namespace *user_ns;
>  	struct work_struct proc_work;
> -	kgid_t pid_gid;
> -	int hide_pid;
>  	int reboot;	/* group exit code if this pidns was rebooted */
>  	unsigned int proc_inum;
>  };
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Stephen Mell]

On Thursday, May 23, 2013 18:20:57 Gu Zheng wrote:

> Here it'll create a new proc sb instance which holds the same context as the old ones
> each time we mount proc though in the same PID namespace, won't it?
I believe so. But this is the point, right? They won't be identical if different mount options are used, I don't think.

> Here the pre-check seems needless.
Is that new with my patch, or has it always been needless?

Thanks,
Stephen

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Gu Zheng]

Hi Stephen,

On 05/24/2013 07:32 AM, Stephen Mell wrote:

> On Thursday, May 23, 2013 18:20:57 Gu Zheng wrote:
> 
>> Here it'll create a new proc sb instance which holds the same context as the old ones
>> each time we mount proc though in the same PID namespace, won't it?
> I believe so. But this is the point, right? 

Yes, but I think it's also the problem.

>They won't be identical if different mount options are used, I don't think.

If different mount options are used, we'll create different super block instance, and they have
the same context, only the difference is each one holds different proc_sb_info.
But I think what we really want is only one proc sb instance and create different proc_sb_info
if different mount options are used.

> 
>> Here the pre-check seems needless.
> Is that new with my patch, or has it always been needless?

Yeah, it's always needless.

Thanks,
Gu

> 
> Thanks,
> Stephen
> 

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Stephen Mell]

Gu,

On Friday, May 24, 2013 11:03:31 Gu Zheng wrote:
> Hi Stephen,
> 
> On 05/24/2013 07:32 AM, Stephen Mell wrote:
> 
> > On Thursday, May 23, 2013 18:20:57 Gu Zheng wrote:
> > 
> >> Here it'll create a new proc sb instance which holds the same context as the old ones
> >> each time we mount proc though in the same PID namespace, won't it?
> > I believe so. But this is the point, right? 

> Yes, but I think it's also the problem.
> 
> >They won't be identical if different mount options are used, I don't think.
> 
> If different mount options are used, we'll create different super block instance, and they have
> the same context, only the difference is each one holds different proc_sb_info.
> But I think what we really want is only one proc sb instance and create different proc_sb_info
> if different mount options are used.

Will having several different superblocks cause problems, or is it merely inefficient? I freely admit to not really knowing what I'm doing, and I thank you for your assistance.
How is this situation distinct from that of ramfs? It appears to have a superblock for each mount.
It would seem to me as though one cannot have different sb_infos with the same superblock, making storing the mount options in sb_info effectively the same as storing them in the superblock itself, for the purposes of this discussion. Where would the mount options be stored, if not in the superblock?

> > 
> >> Here the pre-check seems needless.
> > Is that new with my patch, or has it always been needless?
> 
> Yeah, it's always needless.
> 
> Thanks,
> Gu
> 
> > 
> > Thanks,
> > Stephen

Thanks again,
Stephen

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Gu Zheng]

Hi Stephen,

On 05/24/2013 12:29 PM, Stephen Mell wrote:

> Gu,
> 
> On Friday, May 24, 2013 11:03:31 Gu Zheng wrote:
>> Hi Stephen,
>>
>> On 05/24/2013 07:32 AM, Stephen Mell wrote:
>>
>>> On Thursday, May 23, 2013 18:20:57 Gu Zheng wrote:
>>>
>>>> Here it'll create a new proc sb instance which holds the same context as the old ones
>>>> each time we mount proc though in the same PID namespace, won't it?
>>> I believe so. But this is the point, right? 
> 
>> Yes, but I think it's also the problem.
>>
>>> They won't be identical if different mount options are used, I don't think.
>>
>> If different mount options are used, we'll create different super block instance, and they have
>> the same context, only the difference is each one holds different proc_sb_info.
>> But I think what we really want is only one proc sb instance and create different proc_sb_info
>> if different mount options are used.
> 
> Will having several different superblocks cause problems, or is it merely inefficient? 

Not only inefficient.

>I freely admit to not really knowing what I'm doing, and I thank you for your assistance.
> How is this situation distinct from that of ramfs? It appears to have a superblock for each mount.

They're different, each ramfs uses a split superblock to manage it's infos, e.g. the usage, and each ramfs mount instance should not affect others.
But proc is a common interface, each mount instance holds the same context, so there's no need to create a new superblock instance each time mount if we in
the same PID namespace. 

> It would seem to me as though one cannot have different sb_infos with the same superblock, making storing the mount options in sb_info effectively the same as storing them in the superblock itself, for the purposes of this discussion. Where would the mount options be stored, if not in the superblock?
> 

One fuzzy way in my mind, I'm not sure whether it's OK, but we can discuss it.
Split hide_pid, pid_gid, and proc_self from pid_namespace, and create struct proc_sb_info(maybe the name "proc_mount_info" is better). 
And create a new list domain in the pid_namespace to contain the proc_sb_info instances. Each time we mount proc in a new directory only
create a new proc_sb_info instance, and added it to the list in pid_namespace. 
But this leads to another problem, how to get the right proc_sb_info instance in proc permission checking routine, do you have any idea?
what do you think of this way?


Thanks,
Gu

>>>
>>>> Here the pre-check seems needless.
>>> Is that new with my patch, or has it always been needless?
>>
>> Yeah, it's always needless.
>>
>> Thanks,
>> Gu
>>
>>>
>>> Thanks,
>>> Stephen
> 
> Thanks again,
> Stephen
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Stephen Mell]

On Friday, May 24, 2013 17:14:13 Gu Zheng wrote:

> One fuzzy way in my mind, I'm not sure whether it's OK, but we can discuss it.
> Split hide_pid, pid_gid, and proc_self from pid_namespace, and create struct proc_sb_info(maybe the name "proc_mount_info" is better). 
> And create a new list domain in the pid_namespace to contain the proc_sb_info instances. Each time we mount proc in a new directory only
> create a new proc_sb_info instance, and added it to the list in pid_namespace. 
> But this leads to another problem, how to get the right proc_sb_info instance in proc permission checking routine, do you have any idea?
> what do you think of this way?

I understand now what you're getting at.
However, I'd like to make the argument that it is desirable to have each proc mount, even those that reference the same namespace, have a different superblock. One option that I intend to add is the ability to specify which pid namespace proc is mounted for, rather than forcing the current one. If this were to be added, it wouldn't work to share superblocks, as that would prevent remounts of proc from switching which namespace that the refer to (or that is my understanding, which may be incorrect).
Considering the small number of proc mounts that tend to be around anyway, perhaps this outweighs the drawbacks.
Let me know what you think.

> Thanks,
> Gu

Thanks,
Stephen

Re: [PATCH] proc: move proc mount options out of pid_namespace

[Gu Zheng]

On 05/24/2013 05:35 PM, Stephen Mell wrote:

> On Friday, May 24, 2013 17:14:13 Gu Zheng wrote:
> 
>> One fuzzy way in my mind, I'm not sure whether it's OK, but we can discuss it.
>> Split hide_pid, pid_gid, and proc_self from pid_namespace, and create struct proc_sb_info(maybe the name "proc_mount_info" is better). 
>> And create a new list domain in the pid_namespace to contain the proc_sb_info instances. Each time we mount proc in a new directory only
>> create a new proc_sb_info instance, and added it to the list in pid_namespace. 
>> But this leads to another problem, how to get the right proc_sb_info instance in proc permission checking routine, do you have any idea?
>> what do you think of this way?
> 
> I understand now what you're getting at.
> However, I'd like to make the argument that it is desirable to have each proc mount, even those that reference the same namespace, have a different superblock. One option that I intend to add is the ability to specify which pid namespace proc is mounted for, rather than forcing the current one. If this were to be added, it wouldn't work to share superblocks, as that would prevent remounts of proc from switching which namespace that the refer to (or that is my understanding, which may be incorrect).
> Considering the small number of proc mounts that tend to be around anyway, perhaps this outweighs the drawbacks.
> Let me know what you think.


It doesn't matter, if we can not find a better way, the current one is best, go ahead!:)

Thanks,
Gu

> 
>> Thanks,
>> Gu
> 
> Thanks,
> Stephen
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
> 

[PATCH] proc: move proc mount options out of pid_namespace

[Stephen Mell]

From: Stephen Mell <sub.atomic.fusion@gmail.com>

hide_pid and pid_gid are proc mount options whose values are stored in the pid_namespace struct. As a result, if one mounts proc again for the same PID namespace with different mount options, all mounts for that PID namespace will be affected. This seems undesirable. This patch creates a proc_sb_info struct that points to the applicable PID namespace, and it moves hide_pid, pid_gid, and proc_self from pid_namespace to proc_sb_info. This patch removes a redundant null pointer check prior to calling dput which it would otherwise have to readd.

Signed-off-by: Stephen Mell <sub.atomic.fusion@gmail.com>
---
 fs/proc/base.c                | 38 +++++++++++++++++----------
 fs/proc/inode.c               | 10 ++++----
 fs/proc/internal.h            |  8 ++++++
 fs/proc/root.c                | 60 +++++++++++++++++++++++++------------------
 fs/proc/self.c                | 10 +++++---
 include/linux/pid_namespace.h |  3 ---
 6 files changed, 78 insertions(+), 51 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index dd51e50..853eb68 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -584,13 +584,13 @@ int proc_setattr(struct dentry *dentry, struct iattr *attr)
  * May current process learn task's sched/cmdline info (for hide_pid_min=1)
  * or euid/egid (for hide_pid_min=2)?
  */
-static bool has_pid_permissions(struct pid_namespace *pid,
+static bool has_pid_permissions(struct proc_sb_info *fsi,
 				 struct task_struct *task,
 				 int hide_pid_min)
 {
-	if (pid->hide_pid < hide_pid_min)
+	if (fsi->hide_pid < hide_pid_min)
 		return true;
-	if (in_group_p(pid->pid_gid))
+	if (in_group_p(fsi->pid_gid))
 		return true;
 	return ptrace_may_access(task, PTRACE_MODE_READ);
 }
@@ -598,18 +598,18 @@ static bool has_pid_permissions(struct pid_namespace *pid,
 
 static int proc_pid_permission(struct inode *inode, int mask)
 {
-	struct pid_namespace *pid = inode->i_sb->s_fs_info;
+	struct proc_sb_info *fsi = inode->i_sb->s_fs_info;
 	struct task_struct *task;
 	bool has_perms;
 
 	task = get_proc_task(inode);
 	if (!task)
 		return -ESRCH;
-	has_perms = has_pid_permissions(pid, task, 1);
+	has_perms = has_pid_permissions(fsi, task, 1);
 	put_task_struct(task);
 
 	if (!has_perms) {
-		if (pid->hide_pid == 2) {
+		if (fsi->hide_pid == 2) {
 			/*
 			 * Let's make getdents(), stat(), and open()
 			 * consistent with each other.  If a process
@@ -670,12 +670,14 @@ static const struct file_operations proc_info_file_operations = {
 static int proc_single_show(struct seq_file *m, void *v)
 {
 	struct inode *inode = m->private;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 	struct pid *pid;
 	struct task_struct *task;
 	int ret;
 
-	ns = inode->i_sb->s_fs_info;
+	fsi = inode->i_sb->s_fs_info;
+	ns = fsi->ns;
 	pid = proc_pid(inode);
 	task = get_pid_task(pid, PIDTYPE_PID);
 	if (!task)
@@ -1574,7 +1576,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	struct inode *inode = dentry->d_inode;
 	struct task_struct *task;
 	const struct cred *cred;
-	struct pid_namespace *pid = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
 
 	generic_fillattr(inode, stat);
 
@@ -1583,7 +1585,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 	stat->gid = GLOBAL_ROOT_GID;
 	task = pid_task(proc_pid(inode), PIDTYPE_PID);
 	if (task) {
-		if (!has_pid_permissions(pid, task, 2)) {
+		if (!has_pid_permissions(fsi, task, 2)) {
 			rcu_read_unlock();
 			/*
 			 * This doesn't prevent learning whether PID exists,
@@ -2869,13 +2871,15 @@ struct dentry *proc_pid_lookup(struct inode *dir, struct dentry * dentry, unsign
 	struct dentry *result = NULL;
 	struct task_struct *task;
 	unsigned tgid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	tgid = name_to_int(dentry);
 	if (tgid == ~0U)
 		goto out;
 
-	ns = dentry->d_sb->s_fs_info;
+	fsi = dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	rcu_read_lock();
 	task = find_task_by_pid_ns(tgid, ns);
 	if (task)
@@ -2954,6 +2958,7 @@ static int fake_filldir(void *buf, const char *name, int namelen,
 int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 {
 	struct tgid_iter iter;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 	filldir_t __filldir;
 	loff_t pos = filp->f_pos;
@@ -2970,11 +2975,12 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
 		iter.tgid = pos - TGID_OFFSET;
 	}
 	iter.task = NULL;
-	ns = filp->f_dentry->d_sb->s_fs_info;
+	fsi = filp->f_dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	for (iter = next_tgid(ns, iter);
 	     iter.task;
 	     iter.tgid += 1, iter = next_tgid(ns, iter)) {
-		if (has_pid_permissions(ns, iter.task, 2))
+		if (has_pid_permissions(fsi, iter.task, 2))
 			__filldir = filldir;
 		else
 			__filldir = fake_filldir;
@@ -3132,6 +3138,7 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
 	struct task_struct *task;
 	struct task_struct *leader = get_proc_task(dir);
 	unsigned tid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	if (!leader)
@@ -3141,7 +3148,8 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
 	if (tid == ~0U)
 		goto out;
 
-	ns = dentry->d_sb->s_fs_info;
+	fsi = dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	rcu_read_lock();
 	task = find_task_by_pid_ns(tid, ns);
 	if (task)
@@ -3249,6 +3257,7 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
 	int retval = -ENOENT;
 	ino_t ino;
 	int tid;
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
 	task = get_proc_task(inode);
@@ -3283,7 +3292,8 @@ static int proc_task_readdir(struct file * filp, void * dirent, filldir_t filldi
 	/* f_version caches the tgid value that the last readdir call couldn't
 	 * return. lseek aka telldir automagically resets f_version to 0.
 	 */
-	ns = filp->f_dentry->d_sb->s_fs_info;
+	fsi = filp->f_dentry->d_sb->s_fs_info;
+	ns = fsi->ns;
 	tid = (int)filp->f_version;
 	filp->f_version = 0;
 	for (task = first_tid(leader, tid, filp->f_pos - 2, ns);
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 073aea6..148737d 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -110,12 +110,12 @@ void __init proc_init_inodecache(void)
 static int proc_show_options(struct seq_file *seq, struct dentry *root)
 {
 	struct super_block *sb = root->d_sb;
-	struct pid_namespace *pid = sb->s_fs_info;
+	struct proc_sb_info *fsi = sb->s_fs_info;
 
-	if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
-		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
-	if (pid->hide_pid != 0)
-		seq_printf(seq, ",hidepid=%u", pid->hide_pid);
+	if (!gid_eq(fsi->pid_gid, GLOBAL_ROOT_GID))
+		seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fsi->pid_gid));
+	if (fsi->hide_pid != 0)
+		seq_printf(seq, ",hidepid=%u", fsi->hide_pid);
 
 	return 0;
 }
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index d600fb0..ff970e4 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -29,6 +29,14 @@ struct mempolicy;
  * /proc file has a parent, but "subdir" is NULL for all
  * non-directory entries).
  */
+
+struct proc_sb_info {
+	struct pid_namespace *ns;
+	struct dentry *proc_self;
+	kgid_t pid_gid;
+	int hide_pid;
+};
+
 struct proc_dir_entry {
 	unsigned int low_ino;
 	umode_t mode;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 41a6ea9..5a2b6ff 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -20,6 +20,7 @@
 #include <linux/mount.h>
 #include <linux/pid_namespace.h>
 #include <linux/parser.h>
+#include <linux/slab.h>
 
 #include "internal.h"
 
@@ -31,10 +32,9 @@ static int proc_test_super(struct super_block *sb, void *data)
 static int proc_set_super(struct super_block *sb, void *data)
 {
 	int err = set_anon_super(sb, NULL);
-	if (!err) {
-		struct pid_namespace *ns = (struct pid_namespace *)data;
-		sb->s_fs_info = get_pid_ns(ns);
-	}
+	if (!err)
+		sb->s_fs_info = (struct proc_sb_info *)data;
+
 	return err;
 }
 
@@ -48,7 +48,7 @@ static const match_table_t tokens = {
 	{Opt_err, NULL},
 };
 
-static int proc_parse_options(char *options, struct pid_namespace *pid)
+static int proc_parse_options(char *options, struct proc_sb_info *fsi)
 {
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
@@ -68,7 +68,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 		case Opt_gid:
 			if (match_int(&args[0], &option))
 				return 0;
-			pid->pid_gid = make_kgid(current_user_ns(), option);
+			fsi->pid_gid = make_kgid(current_user_ns(), option);
 			break;
 		case Opt_hidepid:
 			if (match_int(&args[0], &option))
@@ -77,7 +77,7 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 				pr_err("proc: hidepid value must be between 0 and 2.\n");
 				return 0;
 			}
-			pid->hide_pid = option;
+			fsi->hide_pid = option;
 			break;
 		default:
 			pr_err("proc: unrecognized mount option \"%s\" "
@@ -91,36 +91,44 @@ static int proc_parse_options(char *options, struct pid_namespace *pid)
 
 int proc_remount(struct super_block *sb, int *flags, char *data)
 {
-	struct pid_namespace *pid = sb->s_fs_info;
-	return !proc_parse_options(data, pid);
+	struct proc_sb_info *fsi = sb->s_fs_info;
+	return !proc_parse_options(data, fsi);
 }
 
 static struct dentry *proc_mount(struct file_system_type *fs_type,
 	int flags, const char *dev_name, void *data)
 {
 	int err;
+	struct proc_sb_info *fsi;
 	struct super_block *sb;
-	struct pid_namespace *ns;
 	char *options;
+	
+	fsi = kzalloc(sizeof(struct proc_sb_info), GFP_KERNEL);
+	if (!fsi)
+		return ERR_PTR(-ENOMEM);
+
+	sb = sget(fs_type, proc_test_super, proc_set_super, flags, fsi);
+	if (IS_ERR(sb))
+		return ERR_CAST(sb);
 
 	if (flags & MS_KERNMOUNT) {
-		ns = (struct pid_namespace *)data;
+		fsi->ns = (struct pid_namespace *)data;
+		get_pid_ns(fsi->ns);
 		options = NULL;
 	} else {
-		ns = task_active_pid_ns(current);
-		options = data;
-
 		if (!current_user_ns()->may_mount_proc)
 			return ERR_PTR(-EPERM);
-	}
-
-	sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
-	if (IS_ERR(sb))
-		return ERR_CAST(sb);
+		
+		options = data;
+		if (!proc_parse_options(options, fsi)) {
+			deactivate_locked_super(sb);
+			return ERR_PTR(-EINVAL);
+		}
 
-	if (!proc_parse_options(options, ns)) {
-		deactivate_locked_super(sb);
-		return ERR_PTR(-EINVAL);
+		if (!fsi->ns) {
+			fsi->ns = task_active_pid_ns(current);
+			get_pid_ns(fsi->ns);
+		}
 	}
 
 	if (!sb->s_root) {
@@ -138,13 +146,15 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 
 static void proc_kill_sb(struct super_block *sb)
 {
+	struct proc_sb_info *fsi;
 	struct pid_namespace *ns;
 
-	ns = (struct pid_namespace *)sb->s_fs_info;
-	if (ns->proc_self)
-		dput(ns->proc_self);
+	fsi = (struct proc_sb_info *)sb->s_fs_info;
+	ns = (struct pid_namespace *)fsi->ns;
+	dput(fsi->proc_self);
 	kill_anon_super(sb);
 	put_pid_ns(ns);
+	kfree(fsi);
 }
 
 static struct file_system_type proc_fs_type = {
diff --git a/fs/proc/self.c b/fs/proc/self.c
index 6b6a993..ff4a2e2 100644
--- a/fs/proc/self.c
+++ b/fs/proc/self.c
@@ -10,7 +10,8 @@
 static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 			      int buflen)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = fsi->ns;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char tmp[PROC_NUMBUF];
 	if (!tgid)
@@ -21,7 +22,8 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 
 static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct proc_sb_info *fsi = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = fsi->ns;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char *name = ERR_PTR(-ENOENT);
 	if (tgid) {
@@ -55,7 +57,7 @@ static unsigned self_inum;
 int proc_setup_self(struct super_block *s)
 {
 	struct inode *root_inode = s->s_root->d_inode;
-	struct pid_namespace *ns = s->s_fs_info;
+	struct proc_sb_info *fsi = s->s_fs_info;
 	struct dentry *self;
 	
 	mutex_lock(&root_inode->i_mutex);
@@ -82,7 +84,7 @@ int proc_setup_self(struct super_block *s)
 		pr_err("proc_fill_super: can't allocate /proc/self\n");
 		return PTR_ERR(self);
 	}
-	ns->proc_self = self;
+	fsi->proc_self = self;
 	return 0;
 }
 
diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index e277266..6185386 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -31,15 +31,12 @@ struct pid_namespace {
 	struct pid_namespace *parent;
 #ifdef CONFIG_PROC_FS
 	struct vfsmount *proc_mnt;
-	struct dentry *proc_self;
 #endif
 #ifdef CONFIG_BSD_PROCESS_ACCT
 	struct bsd_acct_struct *bacct;
 #endif
 	struct user_namespace *user_ns;
 	struct work_struct proc_work;
-	kgid_t pid_gid;
-	int hide_pid;
 	int reboot;	/* group exit code if this pidns was rebooted */
 	unsigned int proc_inum;
 };