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Date:	Sat, 25 May 2013 07:32:33 +0000
From:	Stephen Mell <sub.atomic.fusion@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH] proc: move proc mount options out of pid_namespace

From: Stephen Mell <sub.atomic.fusion@...il.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@...il.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;
 };
--
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