proc 2/2: remove struct proc_dir_entry::owner

Setting ->owner as done currently (pde->owner = THIS_MODULE) is racy
as correctly noted at bug #12454. Someone can lookup entry with NULL
->owner, thus not pinning enything, and release it later resulting
in module refcount underflow.

We can keep ->owner and supply it at registration time like ->proc_fops
and ->data.

But this leaves ->owner as easy-manipulative field (just one C assignment)
and somebody will forget to unpin previous/pin current module when
switching ->owner. ->proc_fops is declared as "const" which should give
some thoughts.

->read_proc/->write_proc were just fixed to not require ->owner for
protection.

rmmod'ed directories will be empty and return "." and ".." -- no harm.
And directories with tricky enough readdir and lookup shouldn't be modular.
We definitely don't want such modular code.

Removing ->owner will also make PDE smaller.

So, let's nuke it.

Kudos to Jeff Layton for reminding about this, let's say, oversight.

http://bugzilla.kernel.org/show_bug.cgi?id=12454

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

1 files changed, 2 insertions, 29 deletions

diff --git a/sound/core/info.c b/sound/core/info.c
index 70fa871..35df614 100644
--- a/sound/core/info.c
+++ b/sound/core/info.c
@@ -154,11 +154,6 @@ EXPORT_SYMBOL(snd_seq_root);
 struct snd_info_entry *snd_oss_root;
 #endif
 
-static inline void snd_info_entry_prepare(struct proc_dir_entry *de)
-{
-	de->owner = THIS_MODULE;
-}
-
 static void snd_remove_proc_entry(struct proc_dir_entry *parent,
 				  struct proc_dir_entry *de)
 {
@@ -522,32 +517,11 @@ static const struct file_operations snd_info_entry_operations =
 	.release =		snd_info_entry_release,
 };
 
-/**
- * snd_create_proc_entry - create a procfs entry
- * @name: the name of the proc file
- * @mode: the file permission bits, S_Ixxx
- * @parent: the parent proc-directory entry
- *
- * Creates a new proc file entry with the given name and permission
- * on the given directory.
- *
- * Returns the pointer of new instance or NULL on failure.
- */
-static struct proc_dir_entry *snd_create_proc_entry(const char *name, mode_t mode,
-						    struct proc_dir_entry *parent)
-{
-	struct proc_dir_entry *p;
-	p = create_proc_entry(name, mode, parent);
-	if (p)
-		snd_info_entry_prepare(p);
-	return p;
-}
-
 int __init snd_info_init(void)
 {
 	struct proc_dir_entry *p;
 
-	p = snd_create_proc_entry("asound", S_IFDIR | S_IRUGO | S_IXUGO, NULL);
+	p = create_proc_entry("asound", S_IFDIR | S_IRUGO | S_IXUGO, NULL);
 	if (p == NULL)
 		return -ENOMEM;
 	snd_proc_root = p;
@@ -974,12 +948,11 @@ int snd_info_register(struct snd_info_entry * entry)
 		return -ENXIO;
 	root = entry->parent == NULL ? snd_proc_root : entry->parent->p;
 	mutex_lock(&info_mutex);
-	p = snd_create_proc_entry(entry->name, entry->mode, root);
+	p = create_proc_entry(entry->name, entry->mode, root);
 	if (!p) {
 		mutex_unlock(&info_mutex);
 		return -ENOMEM;
 	}
-	p->owner = entry->module;
 	if (!S_ISDIR(entry->mode))
 		p->proc_fops = &snd_info_entry_operations;
 	p->size = entry->size;