From 1b852bceb0d111e510d1a15826ecc4a19358d512 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Fri, 8 May 2015 23:22:29 -0500
Subject: mnt: Refactor the logic for mounting sysfs and proc in a user
 namespace

Fresh mounts of proc and sysfs are a very special case that works very
much like a bind mount.  Unfortunately the current structure can not
preserve the MNT_LOCK... mount flags.  Therefore refactor the logic
into a form that can be modified to preserve those lock bits.

Add a new filesystem flag FS_USERNS_VISIBLE that requires some mount
of the filesystem be fully visible in the current mount namespace,
before the filesystem may be mounted.

Move the logic for calling fs_fully_visible from proc and sysfs into
fs/namespace.c where it has greater access to mount namespace state.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/namespace.c   | 8 +++++++-
 fs/proc/root.c   | 5 +----
 fs/sysfs/mount.c | 5 +----
 3 files changed, 9 insertions(+), 9 deletions(-)

(limited to 'fs')

diff --git a/fs/namespace.c b/fs/namespace.c
index 1b9e11167bae..8e7edaf60fe1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2332,6 +2332,8 @@ unlock:
 	return err;
 }
 
+static bool fs_fully_visible(struct file_system_type *fs_type);
+
 /*
  * create a new mount for userspace and request it to be added into the
  * namespace's tree
@@ -2363,6 +2365,10 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
 			flags |= MS_NODEV;
 			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
 		}
+		if (type->fs_flags & FS_USERNS_VISIBLE) {
+			if (!fs_fully_visible(type))
+				return -EPERM;
+		}
 	}
 
 	mnt = vfs_kern_mount(type, flags, name, data);
@@ -3164,7 +3170,7 @@ bool current_chrooted(void)
 	return chrooted;
 }
 
-bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type)
 {
 	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
 	struct mount *mnt;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index b7fa4bfe896a..64e1ab64bde6 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -112,9 +112,6 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,
 		ns = task_active_pid_ns(current);
 		options = data;
 
-		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
-			return ERR_PTR(-EPERM);
-
 		/* Does the mounter have privilege over the pid namespace? */
 		if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN))
 			return ERR_PTR(-EPERM);
@@ -159,7 +156,7 @@ static struct file_system_type proc_fs_type = {
 	.name		= "proc",
 	.mount		= proc_mount,
 	.kill_sb	= proc_kill_sb,
-	.fs_flags	= FS_USERNS_MOUNT,
+	.fs_flags	= FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
 };
 
 void __init proc_root_init(void)
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
index 8a49486bf30c..1c6ac6fcee9f 100644
--- a/fs/sysfs/mount.c
+++ b/fs/sysfs/mount.c
@@ -31,9 +31,6 @@ static struct dentry *sysfs_mount(struct file_system_type *fs_type,
 	bool new_sb;
 
 	if (!(flags & MS_KERNMOUNT)) {
-		if (!capable(CAP_SYS_ADMIN) && !fs_fully_visible(fs_type))
-			return ERR_PTR(-EPERM);
-
 		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
 			return ERR_PTR(-EPERM);
 	}
@@ -58,7 +55,7 @@ static struct file_system_type sysfs_fs_type = {
 	.name		= "sysfs",
 	.mount		= sysfs_mount,
 	.kill_sb	= sysfs_kill_sb,
-	.fs_flags	= FS_USERNS_MOUNT,
+	.fs_flags	= FS_USERNS_VISIBLE | FS_USERNS_MOUNT,
 };
 
 int __init sysfs_init(void)
-- 
cgit v1.2.3


From 8c6cf9cc829fcd0b179b59f7fe288941d0e31108 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Fri, 8 May 2015 23:49:47 -0500
Subject: mnt: Modify fs_fully_visible to deal with locked ro nodev and atime

Ignore an existing mount if the locked readonly, nodev or atime
attributes are less permissive than the desired attributes
of the new mount.

On success ensure the new mount locks all of the same readonly, nodev and
atime attributes as the old mount.

The nosuid and noexec attributes are not checked here as this change
is destined for stable and enforcing those attributes causes a
regression in lxc and libvirt-lxc where those applications will not
start and there are no known executables on sysfs or proc and no known
way to create exectuables without code modifications

Cc: stable@vger.kernel.org
Fixes: e51db73532955 ("userns: Better restrictions on when proc and sysfs can be mounted")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/namespace.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

(limited to 'fs')

diff --git a/fs/namespace.c b/fs/namespace.c
index 8e7edaf60fe1..63b9806235e6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2332,7 +2332,7 @@ unlock:
 	return err;
 }
 
-static bool fs_fully_visible(struct file_system_type *fs_type);
+static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags);
 
 /*
  * create a new mount for userspace and request it to be added into the
@@ -2366,7 +2366,7 @@ static int do_new_mount(struct path *path, const char *fstype, int flags,
 			mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV;
 		}
 		if (type->fs_flags & FS_USERNS_VISIBLE) {
-			if (!fs_fully_visible(type))
+			if (!fs_fully_visible(type, &mnt_flags))
 				return -EPERM;
 		}
 	}
@@ -3170,9 +3170,10 @@ bool current_chrooted(void)
 	return chrooted;
 }
 
-static bool fs_fully_visible(struct file_system_type *type)
+static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 {
 	struct mnt_namespace *ns = current->nsproxy->mnt_ns;
+	int new_flags = *new_mnt_flags;
 	struct mount *mnt;
 	bool visible = false;
 
@@ -3191,6 +3192,19 @@ static bool fs_fully_visible(struct file_system_type *type)
 		if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
 			continue;
 
+		/* Verify the mount flags are equal to or more permissive
+		 * than the proposed new mount.
+		 */
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) &&
+		    !(new_flags & MNT_READONLY))
+			continue;
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) &&
+		    !(new_flags & MNT_NODEV))
+			continue;
+		if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) &&
+		    ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
+			continue;
+
 		/* This mount is not fully visible if there are any child mounts
 		 * that cover anything except for empty directories.
 		 */
@@ -3201,6 +3215,10 @@ static bool fs_fully_visible(struct file_system_type *type)
 			if (inode->i_nlink > 2)
 				goto next;
 		}
+		/* Preserve the locked attributes */
+		*new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \
+							MNT_LOCK_NODEV    | \
+							MNT_LOCK_ATIME);
 		visible = true;
 		goto found;
 	next:	;
-- 
cgit v1.2.3


From ceeb0e5d39fcdf4dca2c997bf225c7fc49200b37 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Wed, 7 Jan 2015 08:10:09 -0600
Subject: vfs: Ignore unlocked mounts in fs_fully_visible

Limit the mounts fs_fully_visible considers to locked mounts.
Unlocked can always be unmounted so considering them adds hassle
but no security benefit.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/namespace.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

(limited to 'fs')

diff --git a/fs/namespace.c b/fs/namespace.c
index 63b9806235e6..8c7b8e0941b9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3205,11 +3205,15 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 		    ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
 			continue;
 
-		/* This mount is not fully visible if there are any child mounts
-		 * that cover anything except for empty directories.
+		/* This mount is not fully visible if there are any
+		 * locked child mounts that cover anything except for
+		 * empty directories.
 		 */
 		list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
 			struct inode *inode = child->mnt_mountpoint->d_inode;
+			/* Only worry about locked mounts */
+			if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
+				continue;
 			if (!S_ISDIR(inode->i_mode))
 				goto next;
 			if (inode->i_nlink > 2)
-- 
cgit v1.2.3


From fbabfd0f4ee2e8847bf56edf481249ad1bb8c44d Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Sat, 9 May 2015 15:54:49 -0500
Subject: fs: Add helper functions for permanently empty directories.

To ensure it is safe to mount proc and sysfs I need to check if
filesystems that are mounted on top of them are mounted on truly empty
directories.  Given that some directories can gain entries over time,
knowing that a directory is empty right now is insufficient.

Therefore add supporting infrastructure for permantently empty
directories that proc and sysfs can use when they create mount points
for filesystems and fs_fully_visible can use to test for permanently
empty directories to ensure that nothing will be gained by mounting a
fresh copy of proc or sysfs.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/libfs.c         | 96 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/fs.h |  2 ++
 2 files changed, 98 insertions(+)

(limited to 'fs')

diff --git a/fs/libfs.c b/fs/libfs.c
index cb1fb4b9b637..02813592e121 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1093,3 +1093,99 @@ simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
 	return -EINVAL;
 }
 EXPORT_SYMBOL(simple_nosetlease);
+
+
+/*
+ * Operations for a permanently empty directory.
+ */
+static struct dentry *empty_dir_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	return ERR_PTR(-ENOENT);
+}
+
+static int empty_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
+				 struct kstat *stat)
+{
+	struct inode *inode = d_inode(dentry);
+	generic_fillattr(inode, stat);
+	return 0;
+}
+
+static int empty_dir_setattr(struct dentry *dentry, struct iattr *attr)
+{
+	return -EPERM;
+}
+
+static int empty_dir_setxattr(struct dentry *dentry, const char *name,
+			      const void *value, size_t size, int flags)
+{
+	return -EOPNOTSUPP;
+}
+
+static ssize_t empty_dir_getxattr(struct dentry *dentry, const char *name,
+				  void *value, size_t size)
+{
+	return -EOPNOTSUPP;
+}
+
+static int empty_dir_removexattr(struct dentry *dentry, const char *name)
+{
+	return -EOPNOTSUPP;
+}
+
+static ssize_t empty_dir_listxattr(struct dentry *dentry, char *list, size_t size)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct inode_operations empty_dir_inode_operations = {
+	.lookup		= empty_dir_lookup,
+	.permission	= generic_permission,
+	.setattr	= empty_dir_setattr,
+	.getattr	= empty_dir_getattr,
+	.setxattr	= empty_dir_setxattr,
+	.getxattr	= empty_dir_getxattr,
+	.removexattr	= empty_dir_removexattr,
+	.listxattr	= empty_dir_listxattr,
+};
+
+static loff_t empty_dir_llseek(struct file *file, loff_t offset, int whence)
+{
+	/* An empty directory has two entries . and .. at offsets 0 and 1 */
+	return generic_file_llseek_size(file, offset, whence, 2, 2);
+}
+
+static int empty_dir_readdir(struct file *file, struct dir_context *ctx)
+{
+	dir_emit_dots(file, ctx);
+	return 0;
+}
+
+static const struct file_operations empty_dir_operations = {
+	.llseek		= empty_dir_llseek,
+	.read		= generic_read_dir,
+	.iterate	= empty_dir_readdir,
+	.fsync		= noop_fsync,
+};
+
+
+void make_empty_dir_inode(struct inode *inode)
+{
+	set_nlink(inode, 2);
+	inode->i_mode = S_IFDIR | S_IRUGO | S_IXUGO;
+	inode->i_uid = GLOBAL_ROOT_UID;
+	inode->i_gid = GLOBAL_ROOT_GID;
+	inode->i_rdev = 0;
+	inode->i_size = 2;
+	inode->i_blkbits = PAGE_SHIFT;
+	inode->i_blocks = 0;
+
+	inode->i_op = &empty_dir_inode_operations;
+	inode->i_fop = &empty_dir_operations;
+}
+
+bool is_empty_dir_inode(struct inode *inode)
+{
+	return (inode->i_fop == &empty_dir_operations) &&
+		(inode->i_op == &empty_dir_inode_operations);
+}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2d24eeb8e59c..571aab91bfc0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2780,6 +2780,8 @@ extern struct dentry *simple_lookup(struct inode *, struct dentry *, unsigned in
 extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *);
 extern const struct file_operations simple_dir_operations;
 extern const struct inode_operations simple_dir_inode_operations;
+extern void make_empty_dir_inode(struct inode *inode);
+extern bool is_empty_dir_inode(struct inode *inode);
 struct tree_descr { char *name; const struct file_operations *ops; int mode; };
 struct dentry *d_alloc_name(struct dentry *, const char *);
 extern int simple_fill_super(struct super_block *, unsigned long, struct tree_descr *);
-- 
cgit v1.2.3


From f9bd6733d3f11e24f3949becf277507d422ee1eb Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Sat, 9 May 2015 22:09:14 -0500
Subject: sysctl: Allow creating permanently empty directories that serve as
 mountpoints.

Add a magic sysctl table sysctl_mount_point that when used to
create a directory forces that directory to be permanently empty.

Update the code to use make_empty_dir_inode when accessing permanently
empty directories.

Update the code to not allow adding to permanently empty directories.

Update /proc/sys/fs/binfmt_misc to be a permanently empty directory.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/proc/proc_sysctl.c  | 37 +++++++++++++++++++++++++++++++++++++
 include/linux/sysctl.h |  3 +++
 kernel/sysctl.c        |  8 +-------
 3 files changed, 41 insertions(+), 7 deletions(-)

(limited to 'fs')

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index fea2561d773b..fdda62e6115e 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -19,6 +19,28 @@ static const struct inode_operations proc_sys_inode_operations;
 static const struct file_operations proc_sys_dir_file_operations;
 static const struct inode_operations proc_sys_dir_operations;
 
+/* Support for permanently empty directories */
+
+struct ctl_table sysctl_mount_point[] = {
+	{ }
+};
+
+static bool is_empty_dir(struct ctl_table_header *head)
+{
+	return head->ctl_table[0].child == sysctl_mount_point;
+}
+
+static void set_empty_dir(struct ctl_dir *dir)
+{
+	dir->header.ctl_table[0].child = sysctl_mount_point;
+}
+
+static void clear_empty_dir(struct ctl_dir *dir)
+
+{
+	dir->header.ctl_table[0].child = NULL;
+}
+
 void proc_sys_poll_notify(struct ctl_table_poll *poll)
 {
 	if (!poll)
@@ -187,6 +209,17 @@ static int insert_header(struct ctl_dir *dir, struct ctl_table_header *header)
 	struct ctl_table *entry;
 	int err;
 
+	/* Is this a permanently empty directory? */
+	if (is_empty_dir(&dir->header))
+		return -EROFS;
+
+	/* Am I creating a permanently empty directory? */
+	if (header->ctl_table == sysctl_mount_point) {
+		if (!RB_EMPTY_ROOT(&dir->root))
+			return -EINVAL;
+		set_empty_dir(dir);
+	}
+
 	dir->header.nreg++;
 	header->parent = dir;
 	err = insert_links(header);
@@ -202,6 +235,8 @@ fail:
 	erase_header(header);
 	put_links(header);
 fail_links:
+	if (header->ctl_table == sysctl_mount_point)
+		clear_empty_dir(dir);
 	header->parent = NULL;
 	drop_sysctl_table(&dir->header);
 	return err;
@@ -419,6 +454,8 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
 		inode->i_mode |= S_IFDIR;
 		inode->i_op = &proc_sys_dir_operations;
 		inode->i_fop = &proc_sys_dir_file_operations;
+		if (is_empty_dir(head))
+			make_empty_dir_inode(inode);
 	}
 out:
 	return inode;
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 795d5fea5697..fa7bc29925c9 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -188,6 +188,9 @@ struct ctl_table_header *register_sysctl_paths(const struct ctl_path *path,
 void unregister_sysctl_table(struct ctl_table_header * table);
 
 extern int sysctl_init(void);
+
+extern struct ctl_table sysctl_mount_point[];
+
 #else /* CONFIG_SYSCTL */
 static inline struct ctl_table_header *register_sysctl_table(struct ctl_table * table)
 {
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 2082b1a88fb9..c3eee4c6d6c1 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1531,12 +1531,6 @@ static struct ctl_table vm_table[] = {
 	{ }
 };
 
-#if defined(CONFIG_BINFMT_MISC) || defined(CONFIG_BINFMT_MISC_MODULE)
-static struct ctl_table binfmt_misc_table[] = {
-	{ }
-};
-#endif
-
 static struct ctl_table fs_table[] = {
 	{
 		.procname	= "inode-nr",
@@ -1690,7 +1684,7 @@ static struct ctl_table fs_table[] = {
 	{
 		.procname	= "binfmt_misc",
 		.mode		= 0555,
-		.child		= binfmt_misc_table,
+		.child		= sysctl_mount_point,
 	},
 #endif
 	{
-- 
cgit v1.2.3


From eb6d38d5427b3ad42f5268da0f1dd31bb0af1264 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Mon, 11 May 2015 16:44:25 -0500
Subject: proc: Allow creating permanently empty directories that serve as
 mount points

Add a new function proc_create_mount_point that when used to creates a
directory that can not be added to.

Add a new function is_empty_pde to test if a function is a mount
point.

Update the code to use make_empty_dir_inode when reporting
a permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Update /proc/openprom and /proc/fs/nfsd to be permanently empty directories.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/proc/generic.c  | 23 +++++++++++++++++++++++
 fs/proc/inode.c    |  4 ++++
 fs/proc/internal.h |  6 ++++++
 fs/proc/root.c     |  4 ++--
 4 files changed, 35 insertions(+), 2 deletions(-)

(limited to 'fs')

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index df6327a2b865..e5dee5c3188e 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -373,6 +373,10 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
 		WARN(1, "create '/proc/%s' by hand\n", qstr.name);
 		return NULL;
 	}
+	if (is_empty_pde(*parent)) {
+		WARN(1, "attempt to add to permanently empty directory");
+		return NULL;
+	}
 
 	ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);
 	if (!ent)
@@ -455,6 +459,25 @@ struct proc_dir_entry *proc_mkdir(const char *name,
 }
 EXPORT_SYMBOL(proc_mkdir);
 
+struct proc_dir_entry *proc_create_mount_point(const char *name)
+{
+	umode_t mode = S_IFDIR | S_IRUGO | S_IXUGO;
+	struct proc_dir_entry *ent, *parent = NULL;
+
+	ent = __proc_create(&parent, name, mode, 2);
+	if (ent) {
+		ent->data = NULL;
+		ent->proc_fops = NULL;
+		ent->proc_iops = NULL;
+		if (proc_register(parent, ent) < 0) {
+			kfree(ent);
+			parent->nlink--;
+			ent = NULL;
+		}
+	}
+	return ent;
+}
+
 struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
 					struct proc_dir_entry *parent,
 					const struct file_operations *proc_fops,
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 8272aaba1bb0..e3eb5524639f 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -423,6 +423,10 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 		PROC_I(inode)->pde = de;
 
+		if (is_empty_pde(de)) {
+			make_empty_dir_inode(inode);
+			return inode;
+		}
 		if (de->mode) {
 			inode->i_mode = de->mode;
 			inode->i_uid = de->uid;
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index c835b94c0cd3..aa2781095bd1 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -191,6 +191,12 @@ static inline struct proc_dir_entry *pde_get(struct proc_dir_entry *pde)
 }
 extern void pde_put(struct proc_dir_entry *);
 
+static inline bool is_empty_pde(const struct proc_dir_entry *pde)
+{
+	return S_ISDIR(pde->mode) && !pde->proc_iops;
+}
+struct proc_dir_entry *proc_create_mount_point(const char *name);
+
 /*
  * inode.c
  */
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 64e1ab64bde6..68feb0f70e63 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -179,10 +179,10 @@ void __init proc_root_init(void)
 #endif
 	proc_mkdir("fs", NULL);
 	proc_mkdir("driver", NULL);
-	proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
+	proc_create_mount_point("fs/nfsd"); /* somewhere for the nfsd filesystem to be mounted */
 #if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
 	/* just give it a mountpoint */
-	proc_mkdir("openprom", NULL);
+	proc_create_mount_point("openprom");
 #endif
 	proc_tty_init();
 	proc_mkdir("bus", NULL);
-- 
cgit v1.2.3


From ea015218f2f7ace2dad9cedd21ed95bdba2886d7 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Wed, 13 May 2015 16:09:29 -0500
Subject: kernfs: Add support for always empty directories.

Add a new function kernfs_create_empty_dir that can be used to create
directory that can not be modified.

Update the code to use make_empty_dir_inode when reporting a
permanently empty directory to the vfs.

Update the code to not allow adding to permanently empty directories.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/kernfs/dir.c        | 38 +++++++++++++++++++++++++++++++++++++-
 fs/kernfs/inode.c      |  2 ++
 include/linux/kernfs.h |  3 +++
 3 files changed, 42 insertions(+), 1 deletion(-)

(limited to 'fs')

diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index f131fc23ffc4..47dc636d80ed 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -585,6 +585,9 @@ int kernfs_add_one(struct kernfs_node *kn)
 		goto out_unlock;
 
 	ret = -ENOENT;
+	if (parent->flags & KERNFS_EMPTY_DIR)
+		goto out_unlock;
+
 	if ((parent->flags & KERNFS_ACTIVATED) && !kernfs_active(parent))
 		goto out_unlock;
 
@@ -776,6 +779,38 @@ struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 	return ERR_PTR(rc);
 }
 
+/**
+ * kernfs_create_empty_dir - create an always empty directory
+ * @parent: parent in which to create a new directory
+ * @name: name of the new directory
+ *
+ * Returns the created node on success, ERR_PTR() value on failure.
+ */
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+					    const char *name)
+{
+	struct kernfs_node *kn;
+	int rc;
+
+	/* allocate */
+	kn = kernfs_new_node(parent, name, S_IRUGO|S_IXUGO|S_IFDIR, KERNFS_DIR);
+	if (!kn)
+		return ERR_PTR(-ENOMEM);
+
+	kn->flags |= KERNFS_EMPTY_DIR;
+	kn->dir.root = parent->dir.root;
+	kn->ns = NULL;
+	kn->priv = NULL;
+
+	/* link in */
+	rc = kernfs_add_one(kn);
+	if (!rc)
+		return kn;
+
+	kernfs_put(kn);
+	return ERR_PTR(rc);
+}
+
 static struct dentry *kernfs_iop_lookup(struct inode *dir,
 					struct dentry *dentry,
 					unsigned int flags)
@@ -1247,7 +1282,8 @@ int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
 	mutex_lock(&kernfs_mutex);
 
 	error = -ENOENT;
-	if (!kernfs_active(kn) || !kernfs_active(new_parent))
+	if (!kernfs_active(kn) || !kernfs_active(new_parent) ||
+	    (new_parent->flags & KERNFS_EMPTY_DIR))
 		goto out;
 
 	error = 0;
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c
index 2da8493a380b..756dd56aaf60 100644
--- a/fs/kernfs/inode.c
+++ b/fs/kernfs/inode.c
@@ -296,6 +296,8 @@ static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
 	case KERNFS_DIR:
 		inode->i_op = &kernfs_dir_iops;
 		inode->i_fop = &kernfs_dir_fops;
+		if (kn->flags & KERNFS_EMPTY_DIR)
+			make_empty_dir_inode(inode);
 		break;
 	case KERNFS_FILE:
 		inode->i_size = kn->attr.size;
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 71ecdab1671b..29d1896c3ba5 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -45,6 +45,7 @@ enum kernfs_node_flag {
 	KERNFS_LOCKDEP		= 0x0100,
 	KERNFS_SUICIDAL		= 0x0400,
 	KERNFS_SUICIDED		= 0x0800,
+	KERNFS_EMPTY_DIR	= 0x1000,
 };
 
 /* @flags for kernfs_create_root() */
@@ -285,6 +286,8 @@ void kernfs_destroy_root(struct kernfs_root *root);
 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 					 const char *name, umode_t mode,
 					 void *priv, const void *ns);
+struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
+					    const char *name);
 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
 					 const char *name,
 					 umode_t mode, loff_t size,
-- 
cgit v1.2.3


From 87d2846fcf88113fae2341da1ca9a71f0d916f2c Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Wed, 13 May 2015 16:31:40 -0500
Subject: sysfs: Add support for permanently empty directories to serve as
 mount points.

Add two functions sysfs_create_mount_point and
sysfs_remove_mount_point that hang a permanently empty directory off
of a kobject or remove a permanently emptpy directory hanging from a
kobject.  Export these new functions so modular filesystems can use
them.

Cc: stable@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/sysfs/dir.c        | 34 ++++++++++++++++++++++++++++++++++
 include/linux/sysfs.h | 15 +++++++++++++++
 2 files changed, 49 insertions(+)

(limited to 'fs')

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 0b45ff42f374..94374e435025 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -121,3 +121,37 @@ int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
 
 	return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
 }
+
+/**
+ * sysfs_create_mount_point - create an always empty directory
+ * @parent_kobj:  kobject that will contain this always empty directory
+ * @name: The name of the always empty directory to add
+ */
+int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
+{
+	struct kernfs_node *kn, *parent = parent_kobj->sd;
+
+	kn = kernfs_create_empty_dir(parent, name);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, name);
+		return PTR_ERR(kn);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
+
+/**
+ *	sysfs_remove_mount_point - remove an always empty directory.
+ *	@parent_kobj: kobject that will contain this always empty directory
+ *	@name: The name of the always empty directory to remove
+ *
+ */
+void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
+{
+	struct kernfs_node *parent = parent_kobj->sd;
+
+	kernfs_remove_by_name_ns(parent, name, NULL);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
diff --git a/include/linux/sysfs.h b/include/linux/sysfs.h
index 99382c0df17e..9f65758311a4 100644
--- a/include/linux/sysfs.h
+++ b/include/linux/sysfs.h
@@ -210,6 +210,10 @@ int __must_check sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
 int __must_check sysfs_move_dir_ns(struct kobject *kobj,
 				   struct kobject *new_parent_kobj,
 				   const void *new_ns);
+int __must_check sysfs_create_mount_point(struct kobject *parent_kobj,
+					  const char *name);
+void sysfs_remove_mount_point(struct kobject *parent_kobj,
+			      const char *name);
 
 int __must_check sysfs_create_file_ns(struct kobject *kobj,
 				      const struct attribute *attr,
@@ -298,6 +302,17 @@ static inline int sysfs_move_dir_ns(struct kobject *kobj,
 	return 0;
 }
 
+static inline int sysfs_create_mount_point(struct kobject *parent_kobj,
+					   const char *name)
+{
+	return 0;
+}
+
+static inline void sysfs_remove_mount_point(struct kobject *parent_kobj,
+					    const char *name)
+{
+}
+
 static inline int sysfs_create_file_ns(struct kobject *kobj,
 				       const struct attribute *attr,
 				       const void *ns)
-- 
cgit v1.2.3


From f9bb48825a6b5d02f4cabcc78967c75db903dcdc Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Wed, 13 May 2015 17:35:41 -0500
Subject: sysfs: Create mountpoints with sysfs_create_mount_point

This allows for better documentation in the code and
it allows for a simpler and fully correct version of
fs_fully_visible to be written.

The mount points converted and their filesystems are:
/sys/hypervisor/s390/       s390_hypfs
/sys/kernel/config/         configfs
/sys/kernel/debug/          debugfs
/sys/firmware/efi/efivars/  efivarfs
/sys/fs/fuse/connections/   fusectl
/sys/fs/pstore/             pstore
/sys/kernel/tracing/        tracefs
/sys/fs/cgroup/             cgroup
/sys/kernel/security/       securityfs
/sys/fs/selinux/            selinuxfs
/sys/fs/smackfs/            smackfs

Cc: stable@vger.kernel.org
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 arch/s390/hypfs/inode.c      | 12 ++++--------
 drivers/firmware/efi/efi.c   |  6 ++----
 fs/configfs/mount.c          | 10 ++++------
 fs/debugfs/inode.c           | 11 ++++-------
 fs/fuse/inode.c              |  9 +++------
 fs/pstore/inode.c            | 12 ++++--------
 fs/tracefs/inode.c           |  6 ++----
 kernel/cgroup.c              | 10 ++++------
 security/inode.c             | 10 ++++------
 security/selinux/selinuxfs.c | 11 +++++------
 security/smack/smackfs.c     |  8 ++++----
 11 files changed, 40 insertions(+), 65 deletions(-)

(limited to 'fs')

diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
index d3f896a35b98..2eeb0a0f506d 100644
--- a/arch/s390/hypfs/inode.c
+++ b/arch/s390/hypfs/inode.c
@@ -456,8 +456,6 @@ static const struct super_operations hypfs_s_ops = {
 	.show_options	= hypfs_show_options,
 };
 
-static struct kobject *s390_kobj;
-
 static int __init hypfs_init(void)
 {
 	int rc;
@@ -481,18 +479,16 @@ static int __init hypfs_init(void)
 		rc = -ENODATA;
 		goto fail_hypfs_sprp_exit;
 	}
-	s390_kobj = kobject_create_and_add("s390", hypervisor_kobj);
-	if (!s390_kobj) {
-		rc = -ENOMEM;
+	rc = sysfs_create_mount_point(hypervisor_kobj, "s390");
+	if (rc)
 		goto fail_hypfs_diag0c_exit;
-	}
 	rc = register_filesystem(&hypfs_type);
 	if (rc)
 		goto fail_filesystem;
 	return 0;
 
 fail_filesystem:
-	kobject_put(s390_kobj);
+	sysfs_remove_mount_point(hypervisor_kobj, "s390");
 fail_hypfs_diag0c_exit:
 	hypfs_diag0c_exit();
 fail_hypfs_sprp_exit:
@@ -510,7 +506,7 @@ fail_dbfs_exit:
 static void __exit hypfs_exit(void)
 {
 	unregister_filesystem(&hypfs_type);
-	kobject_put(s390_kobj);
+	sysfs_remove_mount_point(hypervisor_kobj, "s390");
 	hypfs_diag0c_exit();
 	hypfs_sprp_exit();
 	hypfs_vm_exit();
diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 3061bb8629dc..e14363d12690 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -65,7 +65,6 @@ static int __init parse_efi_cmdline(char *str)
 early_param("efi", parse_efi_cmdline);
 
 static struct kobject *efi_kobj;
-static struct kobject *efivars_kobj;
 
 /*
  * Let's not leave out systab information that snuck into
@@ -212,10 +211,9 @@ static int __init efisubsys_init(void)
 		goto err_remove_group;
 
 	/* and the standard mountpoint for efivarfs */
-	efivars_kobj = kobject_create_and_add("efivars", efi_kobj);
-	if (!efivars_kobj) {
+	error = sysfs_create_mount_point(efi_kobj, "efivars");
+	if (error) {
 		pr_err("efivars: Subsystem registration failed.\n");
-		error = -ENOMEM;
 		goto err_remove_group;
 	}
 
diff --git a/fs/configfs/mount.c b/fs/configfs/mount.c
index da94e41bdbf6..bca58da65e2b 100644
--- a/fs/configfs/mount.c
+++ b/fs/configfs/mount.c
@@ -129,8 +129,6 @@ void configfs_release_fs(void)
 }
 
 
-static struct kobject *config_kobj;
-
 static int __init configfs_init(void)
 {
 	int err = -ENOMEM;
@@ -141,8 +139,8 @@ static int __init configfs_init(void)
 	if (!configfs_dir_cachep)
 		goto out;
 
-	config_kobj = kobject_create_and_add("config", kernel_kobj);
-	if (!config_kobj)
+	err = sysfs_create_mount_point(kernel_kobj, "config");
+	if (err)
 		goto out2;
 
 	err = register_filesystem(&configfs_fs_type);
@@ -152,7 +150,7 @@ static int __init configfs_init(void)
 	return 0;
 out3:
 	pr_err("Unable to register filesystem!\n");
-	kobject_put(config_kobj);
+	sysfs_remove_mount_point(kernel_kobj, "config");
 out2:
 	kmem_cache_destroy(configfs_dir_cachep);
 	configfs_dir_cachep = NULL;
@@ -163,7 +161,7 @@ out:
 static void __exit configfs_exit(void)
 {
 	unregister_filesystem(&configfs_fs_type);
-	kobject_put(config_kobj);
+	sysfs_remove_mount_point(kernel_kobj, "config");
 	kmem_cache_destroy(configfs_dir_cachep);
 	configfs_dir_cachep = NULL;
 }
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index c1e7ffb0dab6..12756040ca20 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -716,20 +716,17 @@ bool debugfs_initialized(void)
 }
 EXPORT_SYMBOL_GPL(debugfs_initialized);
 
-
-static struct kobject *debug_kobj;
-
 static int __init debugfs_init(void)
 {
 	int retval;
 
-	debug_kobj = kobject_create_and_add("debug", kernel_kobj);
-	if (!debug_kobj)
-		return -EINVAL;
+	retval = sysfs_create_mount_point(kernel_kobj, "debug");
+	if (retval)
+		return retval;
 
 	retval = register_filesystem(&debug_fs_type);
 	if (retval)
-		kobject_put(debug_kobj);
+		sysfs_remove_mount_point(kernel_kobj, "debug");
 	else
 		debugfs_registered = true;
 
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 082ac1c97f39..18dacf9ed8ff 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -1238,7 +1238,6 @@ static void fuse_fs_cleanup(void)
 }
 
 static struct kobject *fuse_kobj;
-static struct kobject *connections_kobj;
 
 static int fuse_sysfs_init(void)
 {
@@ -1250,11 +1249,9 @@ static int fuse_sysfs_init(void)
 		goto out_err;
 	}
 
-	connections_kobj = kobject_create_and_add("connections", fuse_kobj);
-	if (!connections_kobj) {
-		err = -ENOMEM;
+	err = sysfs_create_mount_point(fuse_kobj, "connections");
+	if (err)
 		goto out_fuse_unregister;
-	}
 
 	return 0;
 
@@ -1266,7 +1263,7 @@ static int fuse_sysfs_init(void)
 
 static void fuse_sysfs_cleanup(void)
 {
-	kobject_put(connections_kobj);
+	sysfs_remove_mount_point(fuse_kobj, "connections");
 	kobject_put(fuse_kobj);
 }
 
diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index dc43b5f29305..3adcc4669fac 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -461,22 +461,18 @@ static struct file_system_type pstore_fs_type = {
 	.kill_sb	= pstore_kill_sb,
 };
 
-static struct kobject *pstore_kobj;
-
 static int __init init_pstore_fs(void)
 {
-	int err = 0;
+	int err;
 
 	/* Create a convenient mount point for people to access pstore */
-	pstore_kobj = kobject_create_and_add("pstore", fs_kobj);
-	if (!pstore_kobj) {
-		err = -ENOMEM;
+	err = sysfs_create_mount_point(fs_kobj, "pstore");
+	if (err)
 		goto out;
-	}
 
 	err = register_filesystem(&pstore_fs_type);
 	if (err < 0)
-		kobject_put(pstore_kobj);
+		sysfs_remove_mount_point(fs_kobj, "pstore");
 
 out:
 	return err;
diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
index d92bdf3b079a..a43df11a163f 100644
--- a/fs/tracefs/inode.c
+++ b/fs/tracefs/inode.c
@@ -631,14 +631,12 @@ bool tracefs_initialized(void)
 	return tracefs_registered;
 }
 
-static struct kobject *trace_kobj;
-
 static int __init tracefs_init(void)
 {
 	int retval;
 
-	trace_kobj = kobject_create_and_add("tracing", kernel_kobj);
-	if (!trace_kobj)
+	retval = sysfs_create_mount_point(kernel_kobj, "tracing");
+	if (retval)
 		return -EINVAL;
 
 	retval = register_filesystem(&trace_fs_type);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 469dd547770c..e8a5491be756 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1924,8 +1924,6 @@ static struct file_system_type cgroup_fs_type = {
 	.kill_sb = cgroup_kill_sb,
 };
 
-static struct kobject *cgroup_kobj;
-
 /**
  * task_cgroup_path - cgroup path of a task in the first cgroup hierarchy
  * @task: target task
@@ -5044,13 +5042,13 @@ int __init cgroup_init(void)
 			ss->bind(init_css_set.subsys[ssid]);
 	}
 
-	cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);
-	if (!cgroup_kobj)
-		return -ENOMEM;
+	err = sysfs_create_mount_point(fs_kobj, "cgroup");
+	if (err)
+		return err;
 
 	err = register_filesystem(&cgroup_fs_type);
 	if (err < 0) {
-		kobject_put(cgroup_kobj);
+		sysfs_remove_mount_point(fs_kobj, "cgroup");
 		return err;
 	}
 
diff --git a/security/inode.c b/security/inode.c
index 91503b79c5f8..0e37e4fba8fa 100644
--- a/security/inode.c
+++ b/security/inode.c
@@ -215,19 +215,17 @@ void securityfs_remove(struct dentry *dentry)
 }
 EXPORT_SYMBOL_GPL(securityfs_remove);
 
-static struct kobject *security_kobj;
-
 static int __init securityfs_init(void)
 {
 	int retval;
 
-	security_kobj = kobject_create_and_add("security", kernel_kobj);
-	if (!security_kobj)
-		return -EINVAL;
+	retval = sysfs_create_mount_point(kernel_kobj, "security");
+	if (retval)
+		return retval;
 
 	retval = register_filesystem(&fs_type);
 	if (retval)
-		kobject_put(security_kobj);
+		sysfs_remove_mount_point(kernel_kobj, "security");
 	return retval;
 }
 
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index d2787cca1fcb..3d2201413028 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -1853,7 +1853,6 @@ static struct file_system_type sel_fs_type = {
 };
 
 struct vfsmount *selinuxfs_mount;
-static struct kobject *selinuxfs_kobj;
 
 static int __init init_sel_fs(void)
 {
@@ -1862,13 +1861,13 @@ static int __init init_sel_fs(void)
 	if (!selinux_enabled)
 		return 0;
 
-	selinuxfs_kobj = kobject_create_and_add("selinux", fs_kobj);
-	if (!selinuxfs_kobj)
-		return -ENOMEM;
+	err = sysfs_create_mount_point(fs_kobj, "selinux");
+	if (err)
+		return err;
 
 	err = register_filesystem(&sel_fs_type);
 	if (err) {
-		kobject_put(selinuxfs_kobj);
+		sysfs_remove_mount_point(fs_kobj, "selinux");
 		return err;
 	}
 
@@ -1887,7 +1886,7 @@ __initcall(init_sel_fs);
 #ifdef CONFIG_SECURITY_SELINUX_DISABLE
 void exit_sel_fs(void)
 {
-	kobject_put(selinuxfs_kobj);
+	sysfs_remove_mount_point(fs_kobj, "selinux");
 	kern_unmount(selinuxfs_mount);
 	unregister_filesystem(&sel_fs_type);
 }
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index d9682985349e..ac4cac7c661a 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -2241,16 +2241,16 @@ static const struct file_operations smk_revoke_subj_ops = {
 	.llseek		= generic_file_llseek,
 };
 
-static struct kset *smackfs_kset;
 /**
  * smk_init_sysfs - initialize /sys/fs/smackfs
  *
  */
 static int smk_init_sysfs(void)
 {
-	smackfs_kset = kset_create_and_add("smackfs", NULL, fs_kobj);
-	if (!smackfs_kset)
-		return -ENOMEM;
+	int err;
+	err = sysfs_create_mount_point(fs_kobj, "smackfs");
+	if (err)
+		return err;
 	return 0;
 }
 
-- 
cgit v1.2.3


From 7236c85e1be51a9e25ba0f6e087a66ca89605a49 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Wed, 13 May 2015 20:51:09 -0500
Subject: mnt: Update fs_fully_visible to test for permanently empty
 directories

fs_fully_visible attempts to make fresh mounts of proc and sysfs give
the mounter no more access to proc and sysfs than if they could have
by creating a bind mount.  One aspect of proc and sysfs that makes
this particularly tricky is that there are other filesystems that
typically mount on top of proc and sysfs.  As those filesystems are
mounted on empty directories in practice it is safe to ignore them.
However testing to ensure filesystems are mounted on empty directories
has not been something the in kernel data structures have supported so
the current test for an empty directory which checks to see
if nlink <= 2 is a bit lacking.

proc and sysfs have recently been modified to use the new empty_dir
infrastructure to create all of their dedicated mount points.  Instead
of testing for S_ISDIR(inode->i_mode) && i_nlink <= 2 to see if a
directory is empty, test for is_empty_dir_inode(inode).  That small
change guaranteess mounts found on proc and sysfs really are safe to
ignore, because the directories are not only empty but nothing can
ever be added to them.  This guarantees there is nothing to worry
about when mounting proc and sysfs.

Cc: stable@vger.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/namespace.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

(limited to 'fs')

diff --git a/fs/namespace.c b/fs/namespace.c
index 8c7b8e0941b9..02c6875dd945 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3214,9 +3214,8 @@ static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags)
 			/* Only worry about locked mounts */
 			if (!(mnt->mnt.mnt_flags & MNT_LOCKED))
 				continue;
-			if (!S_ISDIR(inode->i_mode))
-				goto next;
-			if (inode->i_nlink > 2)
+			/* Is the directory permanetly empty? */
+			if (!is_empty_dir_inode(inode))
 				goto next;
 		}
 		/* Preserve the locked attributes */
-- 
cgit v1.2.3


From 93e3bce6287e1fb3e60d3324ed08555b5bbafa89 Mon Sep 17 00:00:00 2001
From: Eric W. Biederman
Date: Sun, 24 May 2015 09:25:00 -0500
Subject: vfs: Remove incorrect debugging WARN in prepend_path

The warning message in prepend_path is unclear and outdated.  It was
added as a warning that the mechanism for generating names of pseudo
files had been removed from prepend_path and d_dname should be used
instead.  Unfortunately the warning reads like a general warning,
making it unclear what to do with it.

Remove the warning.  The transition it was added to warn about is long
over, and I added code several years ago which in rare cases causes
the warning to fire on legitimate code, and the warning is now firing
and scaring people for no good reason.

Cc: stable@vger.kernel.org
Reported-by: Ivan Delalande <colona@arista.com>
Reported-by: Omar Sandoval <osandov@osandov.com>
Fixes: f48cfddc6729e ("vfs: In d_path don't call d_dname on a mount point")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
 fs/dcache.c | 11 -----------
 1 file changed, 11 deletions(-)

(limited to 'fs')

diff --git a/fs/dcache.c b/fs/dcache.c
index 656ce522a218..615dfc2aa752 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2927,17 +2927,6 @@ restart:
 				vfsmnt = &mnt->mnt;
 				continue;
 			}
-			/*
-			 * Filesystems needing to implement special "root names"
-			 * should do so with ->d_dname()
-			 */
-			if (IS_ROOT(dentry) &&
-			   (dentry->d_name.len != 1 ||
-			    dentry->d_name.name[0] != '/')) {
-				WARN(1, "Root dentry has weird name <%.*s>\n",
-				     (int) dentry->d_name.len,
-				     dentry->d_name.name);
-			}
 			if (!error)
 				error = is_mounted(vfsmnt) ? 1 : 2;
 			break;
-- 
cgit v1.2.3