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>

7 files changed, 4 insertions, 26 deletions

diff --git a/fs/afs/proc.c b/fs/afs/proc.c
index 7578c1a..8630615 100644
--- a/fs/afs/proc.c
+++ b/fs/afs/proc.c
@@ -146,7 +146,6 @@ int afs_proc_init(void)
 	proc_afs = proc_mkdir("fs/afs", NULL);
 	if (!proc_afs)
 		goto error_dir;
-	proc_afs->owner = THIS_MODULE;
 
 	p = proc_create("cells", 0, proc_afs, &afs_proc_cells_fops);
 	if (!p)
diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index 877e4d9..7f19fef 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -404,7 +404,6 @@ cifs_proc_init(void)
 	if (proc_fs_cifs == NULL)
 		return;
 
-	proc_fs_cifs->owner = THIS_MODULE;
 	proc_create("DebugData", 0, proc_fs_cifs, &cifs_debug_data_proc_fops);
 
 #ifdef CONFIG_CIFS_STATS
diff --git a/fs/jfs/jfs_debug.c b/fs/jfs/jfs_debug.c
index 6a73de84..dd824d9 100644
--- a/fs/jfs/jfs_debug.c
+++ b/fs/jfs/jfs_debug.c
@@ -90,7 +90,6 @@ void jfs_proc_init(void)
 
 	if (!(base = proc_mkdir("fs/jfs", NULL)))
 		return;
-	base->owner = THIS_MODULE;
 
 	for (i = 0; i < NPROCENT; i++)
 		proc_create(Entries[i].name, 0, base, Entries[i].proc_fops);
diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 574158a..2277421 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -1606,8 +1606,6 @@ int __init nfs_fs_proc_init(void)
 	if (!proc_fs_nfs)
 		goto error_0;
 
-	proc_fs_nfs->owner = THIS_MODULE;
-
 	/* a file of servers with which we're dealing */
 	p = proc_create("servers", S_IFREG|S_IRUGO,
 			proc_fs_nfs, &nfs_server_list_fops);
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index e11dc22..d78ade30 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -58,11 +58,8 @@ static void proc_delete_inode(struct inode *inode)
 
 	/* Let go of any associated proc directory entry */
 	de = PROC_I(inode)->pde;
-	if (de) {
-		if (de->owner)
-			module_put(de->owner);
+	if (de)
 		de_put(de);
-	}
 	if (PROC_I(inode)->sysctl)
 		sysctl_head_put(PROC_I(inode)->sysctl);
 	clear_inode(inode);
@@ -449,12 +446,9 @@ struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
 {
 	struct inode * inode;
 
-	if (!try_module_get(de->owner))
-		goto out_mod;
-
 	inode = iget_locked(sb, ino);
 	if (!inode)
-		goto out_ino;
+		return NULL;
 	if (inode->i_state & I_NEW) {
 		inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 		PROC_I(inode)->fd = 0;
@@ -485,16 +479,9 @@ struct inode *proc_get_inode(struct super_block *sb, unsigned int ino,
 			}
 		}
 		unlock_new_inode(inode);
-	} else {
-	       module_put(de->owner);
+	} else
 	       de_put(de);
-	}
 	return inode;
-
-out_ino:
-	module_put(de->owner);
-out_mod:
-	return NULL;
 }			
 
 int proc_fill_super(struct super_block *s)
diff --git a/fs/proc/proc_tty.c b/fs/proc/proc_tty.c
index d153946..4a9e0f6 100644
--- a/fs/proc/proc_tty.c
+++ b/fs/proc/proc_tty.c
@@ -152,7 +152,6 @@ void proc_tty_register_driver(struct tty_driver *driver)
 	if (!ent)
 		return;
 	ent->read_proc = driver->ops->read_proc;
-	ent->owner = driver->owner;
 	ent->data = driver;
 
 	driver->proc_entry = ent;
diff --git a/fs/reiserfs/procfs.c b/fs/reiserfs/procfs.c
index d506640..9229e55 100644
--- a/fs/reiserfs/procfs.c
+++ b/fs/reiserfs/procfs.c
@@ -492,7 +492,6 @@ int reiserfs_proc_info_init(struct super_block *sb)
 	spin_lock_init(&__PINFO(sb).lock);
 	REISERFS_SB(sb)->procdir = proc_mkdir(b, proc_info_root);
 	if (REISERFS_SB(sb)->procdir) {
-		REISERFS_SB(sb)->procdir->owner = THIS_MODULE;
 		REISERFS_SB(sb)->procdir->data = sb;
 		add_file(sb, "version", show_version);
 		add_file(sb, "super", show_super);
@@ -556,9 +555,7 @@ int reiserfs_proc_info_global_init(void)
 {
 	if (proc_info_root == NULL) {
 		proc_info_root = proc_mkdir(proc_info_root_name, NULL);
-		if (proc_info_root) {
-			proc_info_root->owner = THIS_MODULE;
-		} else {
+		if (!proc_info_root) {
 			reiserfs_warning(NULL, "cannot create /proc/%s",
 					 proc_info_root_name);
 			return 1;