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, 0 insertions, 9 deletions

diff --git a/Documentation/DocBook/procfs_example.c b/Documentation/DocBook/procfs_example.c
index 8c6396e4bf31..a5b11793b1e0 100644
--- a/Documentation/DocBook/procfs_example.c
+++ b/Documentation/DocBook/procfs_example.c
@@ -117,9 +117,6 @@ static int __init init_procfs_example(void)
                 rv = -ENOMEM;
                 goto out;
         }
-        
-        example_dir->owner = THIS_MODULE;
-        
         /* create jiffies using convenience function */
         jiffies_file = create_proc_read_entry("jiffies", 
                                               0444, example_dir, 
@@ -130,8 +127,6 @@ static int __init init_procfs_example(void)
                 goto no_jiffies;
         }
 
-        jiffies_file->owner = THIS_MODULE;
-
         /* create foo and bar files using same callback
          * functions 
          */
@@ -146,7 +141,6 @@ static int __init init_procfs_example(void)
         foo_file->data = &foo_data;
         foo_file->read_proc = proc_read_foobar;
         foo_file->write_proc = proc_write_foobar;
-        foo_file->owner = THIS_MODULE;
                 
         bar_file = create_proc_entry("bar", 0644, example_dir);
         if(bar_file == NULL) {
@@ -159,7 +153,6 @@ static int __init init_procfs_example(void)
         bar_file->data = &bar_data;
         bar_file->read_proc = proc_read_foobar;
         bar_file->write_proc = proc_write_foobar;
-        bar_file->owner = THIS_MODULE;
                 
         /* create symlink */
         symlink = proc_symlink("jiffies_too", example_dir, 
@@ -169,8 +162,6 @@ static int __init init_procfs_example(void)
                 goto no_symlink;
         }
 
-        symlink->owner = THIS_MODULE;
-
         /* everything OK */
         printk(KERN_INFO "%s %s initialised\n",
                MODULE_NAME, MODULE_VERS);