From b6cdc7310338e204224f865918f774eb6db0b75d Mon Sep 17 00:00:00 2001
From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sat, 30 Mar 2013 21:20:14 -0400
Subject: [PATCH] procfs: don't allow to use proc_create, create_proc_entry,
 etc. for directories

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/proc/generic.c | 57 +++++++++++++++++++++--------------------------
 fs/proc/inode.c   |  4 ++--
 2 files changed, 27 insertions(+), 34 deletions(-)

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 21e1a8f1659d..6bce60703c76 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -541,19 +541,18 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
 		return ret;
 
 	if (S_ISDIR(dp->mode)) {
-		if (dp->proc_iops == NULL) {
-			dp->proc_fops = &proc_dir_operations;
-			dp->proc_iops = &proc_dir_inode_operations;
-		}
+		dp->proc_fops = &proc_dir_operations;
+		dp->proc_iops = &proc_dir_inode_operations;
 		dir->nlink++;
 	} else if (S_ISLNK(dp->mode)) {
-		if (dp->proc_iops == NULL)
-			dp->proc_iops = &proc_link_inode_operations;
+		dp->proc_iops = &proc_link_inode_operations;
 	} else if (S_ISREG(dp->mode)) {
 		if (dp->proc_fops == NULL)
 			dp->proc_fops = &proc_file_operations;
-		if (dp->proc_iops == NULL)
-			dp->proc_iops = &proc_file_inode_operations;
+		dp->proc_iops = &proc_file_inode_operations;
+	} else {
+		WARN_ON(1);
+		return -EINVAL;
 	}
 
 	spin_lock(&proc_subdir_lock);
@@ -680,21 +679,19 @@ struct proc_dir_entry *create_proc_entry(const char *name, umode_t mode,
 					 struct proc_dir_entry *parent)
 {
 	struct proc_dir_entry *ent;
-	nlink_t nlink;
 
-	if (S_ISDIR(mode)) {
-		if ((mode & S_IALLUGO) == 0)
-			mode |= S_IRUGO | S_IXUGO;
-		nlink = 2;
-	} else {
-		if ((mode & S_IFMT) == 0)
-			mode |= S_IFREG;
-		if ((mode & S_IALLUGO) == 0)
-			mode |= S_IRUGO;
-		nlink = 1;
+	if ((mode & S_IFMT) == 0)
+		mode |= S_IFREG;
+
+	if (!S_ISREG(mode)) {
+		WARN_ON(1);	/* use proc_mkdir(), damnit */
+		return NULL;
 	}
 
-	ent = __proc_create(&parent, name, mode, nlink);
+	if ((mode & S_IALLUGO) == 0)
+		mode |= S_IRUGO;
+
+	ent = __proc_create(&parent, name, mode, 1);
 	if (ent) {
 		if (proc_register(parent, ent) < 0) {
 			kfree(ent);
@@ -711,21 +708,17 @@ struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
 					void *data)
 {
 	struct proc_dir_entry *pde;
-	nlink_t nlink;
+	if ((mode & S_IFMT) == 0)
+		mode |= S_IFREG;
 
-	if (S_ISDIR(mode)) {
-		if ((mode & S_IALLUGO) == 0)
-			mode |= S_IRUGO | S_IXUGO;
-		nlink = 2;
-	} else {
-		if ((mode & S_IFMT) == 0)
-			mode |= S_IFREG;
-		if ((mode & S_IALLUGO) == 0)
-			mode |= S_IRUGO;
-		nlink = 1;
+	if (!S_ISREG(mode)) {
+		WARN_ON(1);	/* use proc_mkdir() */
+		return NULL;
 	}
 
-	pde = __proc_create(&parent, name, mode, nlink);
+	if ((mode & S_IALLUGO) == 0)
+		mode |= S_IRUGO;
+	pde = __proc_create(&parent, name, mode, 1);
 	if (!pde)
 		goto out;
 	pde->proc_fops = proc_fops;
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 908e97457319..a4aaaeee3342 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -462,8 +462,8 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 			inode->i_size = de->size;
 		if (de->nlink)
 			set_nlink(inode, de->nlink);
-		if (de->proc_iops)
-			inode->i_op = de->proc_iops;
+		WARN_ON(!de->proc_iops);
+		inode->i_op = de->proc_iops;
 		if (de->proc_fops) {
 			if (S_ISREG(inode->i_mode)) {
 #ifdef CONFIG_COMPAT
-- 
2.20.1