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Commit eb6d38d5 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

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: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent f9bd6733

fs/proc/generic.c

+23 −0
Original line number Diff line number Diff line
@@ -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,

fs/proc/inode.c

+4 −0
Original line number Diff line number Diff line
@@ -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;

fs/proc/internal.h

+6 −0
Original line number Diff line number Diff line
@@ -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

 */

fs/proc/root.c

+2 −2
Original line number Diff line number Diff line
@@ -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);