partially fix up the lookup_one_noperm mess

Try to fix the mess created by sysfs braindamage.

 - refactor code internal to fs/namei.c a little to avoid too much
   duplication:
	o __lookup_hash_kern is renamed back to __lookup_hash
	o the old __lookup_hash goes away, permission checks moves to
	  the two callers
	o useless inline qualifiers on above functions go away
 - lookup_one_len_kern loses it's last argument and is renamed to
   lookup_one_noperm to make it's useage a little more clear
 - added kerneldoc comments to describe lookup_one_len aswell as
   lookup_one_noperm and make it very clear that no one should use
   the latter ever.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Josef 'Jeff' Sipek <jsipek@cs.sunysb.edu>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 37 insertions, 24 deletions

diff --git a/fs/namei.c b/fs/namei.c
index b40b808..bab0d19 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1273,7 +1273,8 @@ int __user_path_lookup_open(const char __user *name, unsigned int lookup_flags,
 	return err;
 }
 
-static inline struct dentry *__lookup_hash_kern(struct qstr *name, struct dentry *base, struct nameidata *nd)
+static struct dentry *__lookup_hash(struct qstr *name,
+		struct dentry *base, struct nameidata *nd)
 {
 	struct dentry *dentry;
 	struct inode *inode;
@@ -1313,31 +1314,18 @@ out:
  * needs parent already locked. Doesn't follow mounts.
  * SMP-safe.
  */
-static inline struct dentry * __lookup_hash(struct qstr *name, struct dentry *base, struct nameidata *nd)
+static struct dentry *lookup_hash(struct nameidata *nd)
 {
-	struct dentry *dentry;
-	struct inode *inode;
 	int err;
 
-	inode = base->d_inode;
-
-	err = permission(inode, MAY_EXEC, nd);
-	dentry = ERR_PTR(err);
+	err = permission(nd->dentry->d_inode, MAY_EXEC, nd);
 	if (err)
-		goto out;
-
-	dentry = __lookup_hash_kern(name, base, nd);
-out:
-	return dentry;
-}
-
-static struct dentry *lookup_hash(struct nameidata *nd)
-{
+		return ERR_PTR(err);
 	return __lookup_hash(&nd->last, nd->dentry, nd);
 }
 
-/* SMP-safe */
-static inline int __lookup_one_len(const char *name, struct qstr *this, struct dentry *base, int len)
+static int __lookup_one_len(const char *name, struct qstr *this,
+		struct dentry *base, int len)
 {
 	unsigned long hash;
 	unsigned int c;
@@ -1358,6 +1346,17 @@ static inline int __lookup_one_len(const char *name, struct qstr *this, struct d
 	return 0;
 }
 
+/**
+ * lookup_one_len:  filesystem helper to lookup single pathname component
+ * @name:	pathname component to lookup
+ * @base:	base directory to lookup from
+ * @len:	maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem useage and should
+ * not be called by generic code.  Also note that by using this function to
+ * nameidata argument is passed to the filesystem methods and a filesystem
+ * using this helper needs to be prepared for that.
+ */
 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
 {
 	int err;
@@ -1366,18 +1365,33 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
 	err = __lookup_one_len(name, &this, base, len);
 	if (err)
 		return ERR_PTR(err);
+
+	err = permission(base->d_inode, MAY_EXEC, NULL);
+	if (err)
+		return ERR_PTR(err);
 	return __lookup_hash(&this, base, NULL);
 }
 
-struct dentry *lookup_one_len_kern(const char *name, struct dentry *base, int len)
+/**
+ * lookup_one_noperm - bad hack for sysfs
+ * @name:	pathname component to lookup
+ * @base:	base directory to lookup from
+ *
+ * This is a variant of lookup_one_len that doesn't perform any permission
+ * checks.   It's a horrible hack to work around the braindead sysfs
+ * architecture and should not be used anywhere else.
+ *
+ * DON'T USE THIS FUNCTION EVER, thanks.
+ */
+struct dentry *lookup_one_noperm(const char *name, struct dentry *base)
 {
 	int err;
 	struct qstr this;
 
-	err = __lookup_one_len(name, &this, base, len);
+	err = __lookup_one_len(name, &this, base, strlen(name));
 	if (err)
 		return ERR_PTR(err);
-	return __lookup_hash_kern(&this, base, NULL);
+	return __lookup_hash(&this, base, NULL);
 }
 
 int fastcall __user_walk_fd(int dfd, const char __user *name, unsigned flags,
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 9161db4..d3118d4 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -112,8 +112,7 @@ struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
 		/* look it up */
 		parent = dentry;
 		mutex_lock(&parent->d_inode->i_mutex);
-		dentry = lookup_one_len_kern(cur->s_name, parent,
-					     strlen(cur->s_name));
+		dentry = lookup_one_noperm(cur->s_name, parent);
 		mutex_unlock(&parent->d_inode->i_mutex);
 		dput(parent);